Appendix A collects all the Sonic Pi articles written for the MagPi magazine.

Dive into Topics

These articles aren’t meant to be read in any strict order and contain a lot of cross-over material from the tutorial itself. Rather than try and teach you all of Sonic Pi, they instead each focus on a specific aspect of Sonic Pi and cover it in a fun and accessible way.

Read the MagPi

You can see them in their glorious professionally typeset form in the free PDF downloads of The MagPi here: https://www.raspberrypi.org/magpi/

Suggest a Topic

If you don’t see a topic that interests you covered in these articles - why not suggest one? The easiest way to do that is to tweet your suggestion to @Sonic_Pi. You never know - your suggestion might be the subject of the next article!

1. There are no mistakes

The most important lesson to learn with Sonic Pi is that there really are no mistakes. The best way to learn is to just try and try and try. Try lots of different things out, stop worrying whether your code sounds good or not and start experimenting with as many different synths, notes, FX and opts as possible. You’ll discover a lot of things that make you laugh because they sound just awful and some real gems that sound truly amazing. Simply drop the things you don’t like and keep the things you do. The more ‘mistakes’ you allow yourself to make the quicker you’ll learn and discover your personal coding sound.

2. Use the FX

Say you’ve already mastered the Sonic Pi basics of making sounds with sample, play? What’s next? Did you know that Sonic Pi supports over 27 studio FX to change the sound of your code? FX are like fancy image filters in drawing programs except that instead of blurring or making something black and white, you can add things like reverb, distortion and echo to your sound. Think of it like sticking the cable from your guitar to an effects pedal of your choice and then into the amplifier. Luckily, Sonic Pi makes using FX really easy and requires no cables! All you need to do is to choose which section of your code you’d like the FX added to and wrap it with the FX code. Let’s look at an example. Say you had the following code:

If you wanted to add FX to the :loop_garzul sample, you’d just tuck it inside a with_fx block like this:

Now, if you wanted to add FX to the bass drum, go and wrap that with with_fx too:

Remember, you can wrap any code within with_fx and any sounds created will pass through that FX.

3. Parameterise your synths

In order to really discover your coding sound you’ll soon want to know how to modify and control synths and FX. For example, you might want to change the duration of a note, add more reverb, or change the time between echoes. Luckily, Sonic Pi gives you an amazing level of control to do exactly this with special things called optional parameters or opts for short. Let’s take a quick look. Copy this code into a workspace and hit run:

Ooh, a lovely guitar sound! Now, let’s start playing with it. How about changing its rate?

Hey, what’s that rate: 0.5 bit I just added at the end? That’s called an opt. All of Sonic Pi’s synths and FX support them and there’s loads to play around with. They’re also available for FX too. Try this:

Now, try increasing that feedback to 1 to hear some fun sounds! Read the docs for full details on all the many opts available to you.

4. Live Code

The best way to quickly experiment and explore Sonic Pi is to live code. This allows you to start off some code and continually change and tweak it whilst it’s still playing. For example, if you don’t know what the cutoff parameter does to a sample, just play around. Let’s have a try! Copy this code into one of your Sonic Pi workspaces:

Now, hit run and you’ll hear a slightly muffled drum break. Now, change the cutoff: value to 80 and hit run again. Can you hear the difference? Try 90, 100, 110…

Once you get the hang of using live_loops you’ll not turn back. Whenever I do a live coding gig I rely on live_loop as much as a drummer relies on their sticks. For more information about live coding check out Section 9 of the built-in tutorial.

5. Surf the random streams

Finally, one thing I love doing is cheating by getting Sonic Pi to compose things for me. A really great way to do this is using randomisation. It might sound complicated but it really isn’t. Let’s take a look. Copy this into a spare workspace:

Now, when you play this, you’ll hear a constant stream of random notes from the scale :e2 :minor_pentatonic played with the :dsaw synth. “Wait, wait! That’s not a melody”, I hear you shout! Well, here’s the first part of the magic trick. Every time we go round the live_loop we can tell Sonic Pi to reset the random stream to a known point. This is a bit like going back in time in the TARDIS with the Doctor to a particular point in time and space. Let’s try it - add the line use_random_seed 1 to the live_loop:

Now, every time the live_loop loops around, the random stream is reset. This means it chooses the same 16 notes every time. Hey presto! An instant melody. Now, here’s the really exciting bit. Change the seed value from 1 to another number. Say 4923. Wow! Another melody! So, just by changing one number (the random seed), you can explore as many melodic combinations as you can imagine! Now, that’s the magic of code.

The laser beams sliced through the wafts of smoke as the subwoofer pumped bass deep into the bodies of the crowd. The atmosphere was ripe with a heady mix of synths and dancing. However something wasn’t quite right in this nightclub. Projected in bright colours above the DJ booth was futuristic text, moving, dancing, flashing. This wasn’t fancy visuals, it was merely a projection of Sonic Pi running on a Raspberry Pi. The occupant of the DJ booth wasn’t spinning disks, they wrote, edited and evaluated code. Live. This is Live Coding.

This may sound like a far fetched story from a futuristic night club but coding music like this is a growing trend and is often described as Live Coding (http://toplap.org). One of the recent directions this approach to music making has taken is the Algorave (http://algorave.com) - events where artists like myself code music for people to dance to. However, you don’t need to be in a nightclub to Live Code - with Sonic Pi v2.6+ you can do it anywhere you can take your Raspberry Pi and a pair of headphones or some speakers. Once you reach the end of this article, you’ll be programming your own beats and modifying them live. Where you go afterwards will only be constrained by your imagination.

Live Loop

The key to live coding with Sonic Pi is mastering the live_loop. Let’s look at one:

There are 4 core ingredients to a live_loop. The first is its name. Our live_loop above is called :beats. You’re free to call your live_loop anything you want. Go wild. Be creative. I often use names that communicate something about the music they’re making to the audience. The second ingredient is the do word which marks where the live_loop starts. The third is the end word which marks where the live_loop finishes, and finally there is the body of the live_loop which describes what the loop is going to repeat - that’s the bit between the do and end. In this case we’re repeatedly playing a bass drum sample and waiting for half a beat. This produces a nice regular bass beat. Go ahead, copy it into an empty Sonic Pi buffer and hit run. Boom, Boom, Boom!.

Redefining On-the-fly

Ok, so what’s so special about the live_loop? So far it just seems like a glorified loop! Well, the beauty of live_loops is that you can redefine them on-the-fly. This means that whilst they’re still running, you can change what they do. This is the secret to live coding with Sonic Pi. Let’s have a play:

Now press the Run button or hit Meta-r. You’re now listening to some gorgeous choir sounds. Now, whilst it’s still playing, change the rate from 0.4 to 0.38. Hit run again. Woah! Did you hear the choir change note? Change it back up to 0.4 to return back to how it was. Now, drop it to 0.2, down to 0.19 and then back up to 0.4. See how changing just one parameter on the fly can give you real control of the music? Now play around with the rate yourself - choose your own values. Try negative numbers, really small numbers and large numbers. Have fun!

Sleeping is important

One of the most important lessons about live_loops is that they need rest. Consider the following live_loop:

If you try running this code, you’ll immediately see Sonic Pi complaining that the live_loop did not sleep. This is a safety system kicking in! Take a moment to think about what this code is asking the computer to do. That’s right, it’s asking the computer to play an infinite amount of choir samples in zero time. Without the safety system the poor computer will try and do this and crash and burn in the process. So remember, your live_loops must contain a sleep.

Combining Sounds

Music is full of things happening at the same time. Drums at the same time as bass at the same time as vocals at the same time as guitars… In computing we call this concurrency and Sonic Pi provides us with an amazingly simple way of playing things at the same time. Simply use more than one live_loop!

Here, we have two live_loops, one looping quickly making beats and another looping slowly making a wild bass sound.

One of the interesting things about using multiple live_loops is that they each manage their own time. This means it’s really easy to create interesting polyrhythmical structures and even play with phasing Steve Reich style. Check this out:

Bringing it all together

In each of these tutorials, we’ll end with a final example in the form of a new piece of music which draws from all of the ideas introduced. Read this code and see if you can imagine what it’s doing. Then, copy it into a fresh Sonic Pi buffer and hit Run and actually hear what it sounds like. Finally, change one of the numbers or comment and uncomment things out. See if you can use this as a starting point for a new performance, and most of all have fun! See you next time…

One of the most exciting and disrupting technical developments in modern music was the invention of samplers. These were boxes that allowed you to record any sound into them and then manipulate and play back those sounds in many interesting ways. For example, you could take an old record, find a drum solo (or break), record it into your sampler and then play it back on repeat at half-speed to provide the foundation for your latest beats. This is how early hip-hop music was born and today it’s almost impossible to find electronic music that doesn’t incorporate samples of some kind. Using samples is a really great way of easily introducing new and interesting elements into your live coded performances.

So where can you get a sampler? Well you already have one - it’s your Raspberry Pi! The built-in live coding app Sonic Pi has an extremely powerful sampler built into its core. Let’s play with it!

The Amen Break

One of the most classic and recognisable drum break samples is called the Amen Break. It was first performed in 1969 in the song “Amen Brother” by the Winstons as part of a drum break. However, it was when it was discovered by early hip-hop musicians in the 80s and used in samplers that it started being heavily used in a wide variety of other styles such as drum and bass, breakbeat, hardcore techno and breakcore.

I’m sure you’re excited to hear that it’s also built right into Sonic Pi. Clear up a buffer and throw in the following code:

Hit Run and boom! You’re listening to one of the most influential drum breaks in the history of dance music. However, this sample wasn’t famous for being played as a one-shot, it was built for being looped.

Beat Stretching

Let’s loop the Amen Break by using our old friend the live_loop introduced in this tutorial last month:

OK, so it is looping, but there’s an annoying pause every time round. That is because we asked it to sleep for 2 beats and with the default BPM of 60 the :loop_amen sample only lasts for 1.753 beats. We therefore have a silence of 2 - 1.753 = 0.247 beats. Even though it’s short, it’s still noticeable.

To fix this issue we can use the beat_stretch: opt to ask Sonic Pi to stretch (or shrink) the sample to match the specified number of beats.

Sonic Pi’s sample and synth fns give you a lot of control via optional parameters such as amp:, cutoff: and release:. However, the term optional parameter is a real mouthful so we just call them opts to keep things nice and simple.

Now we’re dancing! Although, perhaps we want to speed it up or slow it down to suit the mood.

Playing with Time

OK, so what if we want to change styles to old school hip hop or breakcore? One simple way of doing this is to play with time - or in other words mess with the tempo. This is super easy in Sonic Pi - just throw in a use_bpm into your live loop:

Whilst you’re rapping over those slow beats, notice that we’re still sleeping for 2 and our BPM is 30, yet everything is in time. The beat_stretch opt works with the current BPM to make sure everything just works.

Now, here’s the fun part. Whilst the loop is still live, change the 30 in the use_bpm 30 line to 50. Woah, everything just got faster yet kept in time! Try going faster - up to 80, to 120, now go wild and punch in 200!

Filtering

Now we can live loop samples, let’s look at some of the most fun opts provided by the sample synth. First up is cutoff: which controls the cutoff filter of the sampler. By default this is disabled but you can easily turn it on:

Go ahead and change the cutoff: opt. For example, increase it to 100, hit Run and wait for the loop to cycle round to hear the change in the sound. Notice that low values like 50 sound mellow and bassy and high values like 100 and 120 are more full-sounding and raspy. This is because the cutoff: opt will chop out the high frequency parts of the sound just like a lawn-mower chops off the top of the grass. The cutoff: opt is like the length setting - determining how much grass is left over.

Slicing

Another great tool to play with is the slicer FX. This will chop (slice) the sound up. Wrap the sample line with the FX code like this:

Notice how the sound bounces up and down a little more. (You can hear the original sound without the FX by changing the mix: opt to 0.) Now, try playing around with the phase: opt. This is the rate (in beats) of the slicing effect. A smaller value like 0.125 will slice faster and larger values like 0.5 will slice more slowly. Notice that successively halving or doubling the phase: opts val tends to always sound good. Finally, change the wave: opt to one of 0, 1, or 2 and hear how it changes the sound. These are the various wave shapes. 0 is a saw wave, (hard in, fade out) 1 is a square wave (hard in, hard out) and 2 is a triangle wave (fade in, fade out).

Bringing it all together

Finally, let’s go back in time and revisit the early Bristol drum and bass scene with this month’s example. Don’t worry too much about what all this means, just type it in, hit Run, then start live coding it by changing opt numbers and see where you can take it. Please do share what you create! See you next time…

Whether it’s the haunting drift of rumbling oscillators or the detuned punch of saw waves piercing through the mix, the lead synth plays an essential role on any electronic track. In last month’s edition of this tutorial series we covered how to code our beats. In this tutorial we’ll cover how to code up the three core components of a synth riff - the timbre, melody and rhythm.

OK, so power up your Raspberry Pi, crack open Sonic Pi v2.6+ and let’s make some noise!

Timbral Possibilities

An essential part of any synth riff is changing and playing with the timbre of the sounds. We can control the timbre in Sonic Pi in two ways - choosing different synths for a dramatic change and setting the various synth opts for more subtle modifications. We can also use FX, but that’s for another tutorial…

Let’s create a simple live loop where we continually change the current synth:

Take a look at the code. We’re simply ticking through a ring of synth names (this will cycle through each of these in turn repeating the list over and over). We pass this synth name to the use_synth fn (function) which will change the live_loop’s current synth. We also play note :e2 (E at the second octave), with a release time of 0.5 beats (half a second at the default BPM of 60) and with the cutoff: opt set to 100.

Hear how the different synths have very different sounds even though they’re all playing the same note. Now experiment and have a play. Change the release time to bigger and smaller values. For example, change the attack: and release: opts to see how different fade in/out times have a huge impact on the sound. Finally change the cutoff: opt to see how different cutoff values also massively influence the timbre (values between 60 and 130 are good). See how many different sounds you can create by just changing a few values. Once you’ve mastered that, just head to the Synths tab in the Help system for a full list of all the synths and all the available opts each individual synth supports to see just how much power you have under your coding fingertips.

Timbre

Timbre is just a fancy word describing the sound of a sound. If you play the same note with different instruments such as a violin, guitar, or piano, the pitch (how high or low it sounds) would be the same, but the sound quality would be different. That sound quality - the thing which allows you to tell the difference between a piano and a guitar is the timbre.

Melodic Composition

Another important aspect to our lead synth is the choice of notes we want to play. If you already have a good idea, then you can simply create a ring with your notes in and tick through them:

Here, we’ve defined our melody with a ring which includes both notes such as :e3 and rests represented by :r. We’re then using .tick to cycle through each note to give us a repeating riff.

Auto Melody

It’s not always easy to come up with a nice riff from scratch. Instead it’s often easier to ask Sonic Pi for a selection of random riffs and to choose the one you like the best. To do that we need to combine three things: rings, randomisation and random seeds. Let’s look at an example:

There’s a few things going on - let’s look at them in turn. First, we specify that we’re using random seed 3. What does this mean? Well, the useful thing is that when we set the seed, we can predict what the next random value is going to be - it’s the same as it was last time we set the seed to 3! Another useful thing to know is that shuffling a ring of notes works in the same way. In the example above we’re essentially asking for the ‘third shuffle’ in the standard list of shuffles - which is also the same every time as we’re always setting the random seed to the same value right before the shuffle. Finally we’re just ticking through our shuffled notes to play the riff.

Now, here’s where the fun starts. If we change the random seed value to another number, say 3000, we get an entirely different shuffling of the notes. So now it’s extremely easy to explore new melodies. Simply choose the list of notes we want to shuffle (scales are a great starting point) and then choose the seed we want to shuffle with. If we don’t like the melody, just change one of those two things and try again. Repeat until you like what you hear!

Pseudo Randomisation

Sonic Pi’s randomisation is not actually random it’s what’s called pseudo random. Imagine if you were to roll a dice 100 times and write down the result of each roll onto a piece of paper. Sonic Pi has the equivalent of this list of results which it uses when you ask for a random value. Instead of rolling an actual dice, it just picks the next value from the list. Setting the random seed is just jumping to a specific point in that list.

Finding your Rhythm

Another important aspect to our riff is the rhythm - when to play a note and when not to. As we saw above we can use :r in our rings to insert rests. Another very powerful way is to use spreads which we’ll cover in a future tutorial. Today we’ll use randomisation to help us find our rhythm. Instead of playing every note we can use a conditional to play a note with a given probability. Let’s take a look:

A really useful fn to know is one_in which will give us a true or false value with the specified probability. Here, we’re using a value of 2 so on average one time every two calls to one_in it will return true. In other words, 50% of the time it will return true. Using higher values will make it return false more often introducing more space into the riff.

Notice that we’ve added some iteration in here with 16.times. This is because we only want to reset our random seed value every 16 notes so our rhythm repeats every 16 times. This doesn’t affect the shuffling as that is still done immediately after the seed is set. We can use the iteration size to alter the length of the riff. Try changing the 16 to 8 or even 4 or 3 and see how it affects the rhythm of the riff.

Bringing it all together

OK, so let’s combine everything we’ve learned together into one final example. See you next time!

It’s impossible to look through the history of electronic dance music without seeing the enormous impact of the tiny Roland TB-303 synthesiser. It’s the secret sauce behind the original acid bass sound. Those classic squealing and squelching TB-303 bass riffs can be heard from the early Chicago House scene through to more recent electronic artists such as Plastikman, Squarepusher and Aphex Twin.

Interestingly, Roland never intended for the TB-303 to be used in dance music. It was originally created as a practice aid for guitarists. They imagined that people would program them to play bass lines to jam along to. Unfortunately there were a number of problems: they were a little fiddly to program, didn’t sound particularly good as a bass-guitar replacement and were pretty expensive to buy. Deciding to cut their losses, Roland stopped making them after 10,000 units were sold and after a number of years sitting on guitarist’s shelves, they soon could be found in the windows of second hand shops. These lonely discarded TB-303s were waiting to be discovered by a new generation of experimenters who started using them in ways that Roland didn’t imagine to create wild new sounds. Acid House was born.

Although getting your hands on an original TB-303 is not so easy you will be pleased to know that you can turn your Raspberry Pi into one using the power of Sonic Pi. Behold, fire up Sonic Pi and throw this code into an empty buffer and hit Run:

Instant acid bass! Let’s play around…

Squelch that Bass

First, let’s build a live arpeggiator to make things fun. In the last tutorial we looked at how riffs can just be a ring of notes that we tick through one after another, repeating when we get to the end. Let’s create a live loop that does exactly that:

Take a look at each line.

1. On the first line we set the default synth to be tb303 with the use_synth fn.
2. On line two we create a live loop called :squelch which will just loop round and round.
3. Line three is where we create our riff - a ring of notes (E in octaves 1, 2, and 3) which we simply tick through with .tick. We define n to represent the current note in the riff. The equals sign just means to assign the value on the right to the name on the left. This will be different every time round the loop. The first time round, n will be set to :e1. The second time round it will be :e2, followed by :e3, and then back to :e1, cycling round forever.
4. Line four is where we actually trigger our :tb303 synth. We’re passing a few interesting opts here: release:, cutoff:, res: and wave: which we’ll discuss below.
5. Line five is our sleep - we’re asking the live loop to loop round every 0.125s or 8 times a second at the default BPM of 60.
6. Line six is the end to the live loop. This just tells Sonic Pi where the end of the live loop is.

Whilst you’re still figuring out what’s going on, type in the code above and hit the Run button. You should hear the :tb303 kick into action. Now, this is where the action is: let’s start live coding.

Whilst the loop is still live, change the cutoff: opt to 110. Now hit the Run button again. You should hear the sound become a little harsher and more squelchy. Dial in 120 and hit run. Now 130. Listen how higher cutoff values make it sound more piercing and intense. Finally, drop it down to 80 when you feel like a rest. Then repeat as many times as you want. Don’t worry, I’ll still be here…

Another opt worth playing with is res:. This controls the level of resonance of the filter. A high resonance is characteristic of acid bass sounds. We currently have our res: set to 0.8. Try cranking it up to 0.85, then 0.9, and finally 0.95. You might find that a cutoff such as 110 or higher will make the differences easier to hear. Finally go wild and dial in 0.999 for some insane sounds. At a res this high, you’re hearing the cutoff filter resonate so much it starts to make sounds of its own!

Finally, for a big impact on the timbre try changing the wave: opt to 1. This is the choice of source oscillator. The default is 0 which is a sawtooth wave. 1 is a pulse wave and 2 is a triangle wave.

Of course, try different riffs by changing the notes in the ring or even picking notes from scales or chords. Have fun with your first acid bass synth.

Deconstructing the TB-303

The design of the original TB-303 is actually pretty simple. As you can see from the following diagram there’s only 4 core parts.

First is the oscillator wave - the raw ingredients of the sound. In this case we have a square wave. Next there’s the oscillator’s amplitude envelope which controls the amp of the square wave through time. These are accessed in Sonic Pi by the attack:, decay:, sustain: and release: opts along with their level counterparts. For more information read Section 2.4 ‘Duration with Envelopes’ in the built-in tutorial. We then pass our enveloped square wave through a resonant low pass filter. This chops off the higher frequencies as well as having that nice resonance effect. Now this is where the fun starts. The cutoff value of this filter is also controlled by its own envelope! This means we have amazing control over the timbre of the sound by playing with both of these envelopes. Let’s take a look:

For each standard envelope opt, there’s a cutoff_ equivalent opt in the :tb303 synth. So, to change the cutoff attack time we can use the cutoff_attack: opt. Copy the code above into an empty buffer and hit Run. You’ll hear a strange sound warble in and out. Now start to play. Try changing the cutoff_attack: time to 1 and then 0.5. Now try 8.

Notice that I’ve passed everything through a :reverb FX for extra atmosphere - try other FX to see what works!

Bringing it all together

Finally, here’s a piece I composed using the ideas in this tutorial. Copy it into an empty buffer, listen for a while and then start live coding your own changes. See what wild sounds you can make with it! See you next time…

Deprecation Warning Apologies but this article was written back when Minecraft Pi Edition was still part of Raspberry Pi OS and Sonic Pi had built-in support to control it with code. Unfortunately this is no longer the case and the minecraft specific code (mc_* functions) are no longer available in Sonic Pi. However, this article is left here as a memory of what was once possible.

Hello and welcome back! In the previous tutorials we’ve focussed purely on the music possibilities of Sonic Pi - (turning your Raspberry Pi into a performance ready musical instrument). So far we’ve learned how to:

• Live Code - changing the sounds on-the-fly,
• Code some huge beats,
• Generate powerful synth leads,
• Re-create the famous TB-303 acid-bass sound.

There’s so much more to show you (which we will explore in future editions). However, this month, let’s look at something Sonic Pi can do that you probably didn’t realise: control Minecraft.

Hello Minecraft World

OK, let’s get started. Boot up your Raspberry Pi, fire up Minecraft Pi and create a new world. Now start up Sonic Pi and re-size and move your windows so you can see both Sonic Pi and Minecraft Pi at the same time.

In a fresh buffer type the following:

Now, hit Run. Boom! Your message appeared in Minecraft! How easy was that? Now, stop reading this for a moment and play about with your own messages. Have fun!

Sonic Teleporter

Now let’s do some exploring. The standard option is to reach for the mouse and keyboard and start walking around. That works, but it’s pretty slow and boring. It would be far better if we had some sort of teleport machine. Well, thanks to Sonic Pi, we have one. Try this:

Crikey! That was a long way up. If you weren’t in flying-mode then you would have fallen back down all the way to the ground. If you double-tap space to enter flying-mode and teleport again, you’ll stay hovering at the location you zap to.

Now, what do those numbers mean? We have three numbers which describe the coordinates of where in the world we want to go. We give each number a name - x, y and z:

• x - how far left and right (80 in our example)
• y - how high we want to be (40 in our example)
• z - how far forward and back (100 in our example)

By choosing different values for x, y and z we can teleport anywhere in our world. Try it! Choose different numbers and see where you can end up. If the screen goes black it’s because you’ve teleported yourself under the ground or into a mountain. Just choose a higher y value to get back out above land. Keep on exploring until you find somewhere you like…

Using the ideas so far, let’s build a Sonic Teleporter which makes a fun teleport sound whilst it whizzes us across the Minecraft world:

Magic Blocks

Now you’ve found a nice spot, let’s start building. You could do what you’re used to and start clicking the mouse furiously to place blocks under the cursor. Or you could use the magic of Sonic Pi. Try this:

Now look up! There’s a melon in the sky! Take a moment to look at the code. What did we do? On line one we grabbed the current location of Steve as the variables x, y and z. These correspond to our coordinates described above. We use these coordinates in the fn mc_set_block which will place the block of your choosing at the specified coordinates. In order to make something higher up in the sky we just need to increase the y value which is why we add 5 to it. Let’s make a long trail of them:

Now, jump over to Minecraft, make sure you’re in flying-mode (double tap space if not) and fly all around the world. Look behind you to see a pretty trail of melon blocks! See what kind of twisty patterns you can make in the sky.

Live Coding Minecraft

Those of you that have been following this tutorial over the last few months will probably have your minds blown at this point. The trail of melons is pretty cool, but the most exciting part of the previous example is that you can use live_loop with Minecraft! For those that don’t know, live_loop is Sonic Pi’s special magic ability that no other programming language has. It lets you run multiple loops at the same time and allows you to change them whilst they run. They are incredibly powerful and amazing fun. I use live_loops to perform music in nightclubs with Sonic Pi - DJs use discs and I use live_loops :-) However, today we’re going to live code both music and Minecraft.

Let’s get started. Run the code above and start making your melon trail again. Now, without stopping the code, just simply change :melon to :brick and hit run. Hey presto, you’re now making a brick trail. How simple was that! Fancy some music to go with it? Easy. Try this:

Now, whilst that’s playing start changing the code. Change the block types - try :water, :grass or your favourite block type. Also, try changing the cutoff value from 70 to 80 and then up to 100. Isn’t this fun?

Bringing it all together

Let’s combine everything we’ve seen so far with a little extra magic. Let’s combine our teleportation ability with block placing and music to make a Minecraft Music Video. Don’t worry if you don’t understand it all, just type it in and have a play by changing some of the values whilst it’s running live. Have fun and see you next time…

After our brief excursion to the fantastic world of coding Minecraft with Sonic Pi last month, let’s get musical again. Today we’re going to bring a classical operatic dance piece straight into the 21st century using the awesome power of code.

Outrageous and Disruptive

Let’s jump into a time machine back to the year 1875. A composer called Bizet had just finished his latest opera Carmen. Unfortunately like many exciting and disruptive new pieces of music people initially didn’t like it at all because it was too outrageous and different. Sadly Bizet died ten years before the opera gained huge international success and became one of the most famous and frequently performed operas of all time. In sympathy with this tragedy let’s take one of the main themes from Carmen and convert it to a modern format of music that is also too outrageous and different for most people in our time - live coded music!

Decoding the Habanera

Trying to live code the whole opera would be a bit of a challenge for this tutorial, so let’s focus on one of the most famous parts - the bass line to the Habanera:

This may look extremely unreadable to you if you haven’t yet studied music notation. However, as programmers we see music notation as just another form of code - only it represents instructions to a musician instead of a computer. We therefore need to figure out a way of decoding it.

Notes

The notes are arranged from left to right like the words in this magazine but also have different heights. The height on the score represents the pitch of the note. The higher the note on the score, the higher the pitch of the note.

In Sonic Pi we already know how to change the pitch of a note - we either use high or low numbers such as play 75 and play 80 or we use the note names: play :E and play :F. Luckily each of the vertical positions of the musical score represents a specific note name. Take a look at this handy look up table:

Rests

Music scores are an extremely rich and expressive kind of code capable of communicating many things. It therefore shouldn’t come as much of a surprise that musical scores can not only tell you what notes to play but also when not to play notes. In programming this is pretty much equivalent to the idea of nil or null - the absence of a value. In other words not playing a note is like the absence of a note.

If you look closely at the score you’ll see that it’s actually a combination of black dots with lines which represent notes to play and squiggly things which represent the rests. Luckily Sonic Pi has a very handy representation for a rest: :r, so if we run: play :r it actually plays silence! We could also write play :rest, play nil or play false which are all equivalent ways of representing rests.

Rhythm

Finally, there’s one last thing to learn how to decode in the notation - the timings of the notes. In the original notation you’ll see that the notes are connected with thick lines called beams. The second note has two of these beams which means it lasts for a 16th of a beat. The other notes have a single beam which means they last for an 8th of a beat. The rest has two squiggly beams which means it also represents a 16th of the beat.

When we attempt to decode and explore new things a very handy trick is to make everything as similar as possible to try and see any relationships or patterns. For example, when we re-write our notation purely in 16ths you can see that our notation just turns into a nice sequence of notes and rests.

Re-coding the Habanera

We’re now in a position to start translating this bass line to Sonic Pi. Let’s encode these notes and rests in a ring:

Let’s see what this sounds like. Throw it in a live loop and tick through it:

Fabulous, that instantly recognisable riff springs to life through your speakers. It took a lot of effort to get here, but it was worth it - high five!

Moody Synths

Now we have the bass line, let’s re-create some of the ambience of the operatic scene. One synth to try out is :blade which is a moody 80s style synth lead. Let’s try it with the starting note :d passed through a slicer and reverb:

Now, try the other notes in the bass line: :a and :f5. Remember, you don’t need to hit stop, just modify the code whilst the music is playing and hit run again. Also, try different values for the slicer’s phase: opt such as 0.5, 0.75 and 1.

Bringing it all together

Finally, let’s combine all the ideas so far into a new remix of the Habanera. You might notice that I’ve included another part of the bass line as a comment. Once you’ve typed it all into a fresh buffer hit Run to hear the composition. Now, without hitting stop, uncomment the second line by removing the # and hit run again - how marvellous is that! Now, start mashing it around yourself and have fun.

Deprecation Warning Apologies but this article was written back when Minecraft Pi Edition was still part of Raspberry Pi OS and Sonic Pi had built-in support to control it with code. Unfortunately this is no longer the case and the minecraft specific code (mc_* functions) are no longer available in Sonic Pi. However, this article is left here as a memory of what was once possible.

Everyone has played Minecraft. You will all have built amazing structures, designed cunning traps and even created elaborate cart lines controlled by redstone switches. How many of you have performed with Minecraft? We bet you didn’t know that you could use Minecraft to create amazing visuals just like a professional VJ.

If your only way of modifying Minecraft was with the mouse, you’d have a tough time changing things fast enough. Luckily for you your Raspberry Pi comes with a version of Minecraft that can be controlled with code. It also comes with an app called Sonic Pi which makes coding Minecraft not only easy but also incredibly fun.

In today’s article we’ll be showing you some of the tips and tricks that we’ve used to create performances in night clubs and music venues around the world.

Let’s get started…

Getting Started

Let’s start with a simple warm up exercise to refresh ourselves with the basics. First up, crack open your Raspberry Pi and then fire up both Minecraft and Sonic Pi. In Minecraft, create a new world, and in Sonic Pi choose a fresh buffer and write in this code:

Hit the Run button and you’ll see the message over in the Minecraft window. OK, we’re ready to start, let’s have some fun……

Sand Storms

When we’re using Minecraft to create visuals we try and think about what will both look interesting and also be easy to generate from code. One nice trick is to create a sand storm by dropping sand blocks from the sky. For that all we need are a few basic fns:

• sleep - for inserting a delay between actions
• mc_location - to find our current location
• mc_set_block- to place sand blocks at a specific location
• rrand - to allow us to generate random values within a range
• live_loop - to allow us to continually make it rain sand

If you’re unfamiliar with any of the built-in fns such as rrand, just type the word into your buffer, click on it and then hit the keyboard combo Control-i to bring up the built-in documentation. Alternatively you can navigate to the lang tab in the Help system and then look up the fns directly along with all the other exciting things you can do.

Let’s make it rain a little first before unleashing the full power of the storm. Grab your current location and use it to create a few sand blocks up in the sky nearby:

When you hit Run, you might have to look around a little as the blocks may start falling down behind you depending on which direction you’re currently facing. Don’t worry, if you missed them just hit Run again for another batch of sand rain - just make sure you’re looking the right way!

Let’s quickly review what’s going on here. On the first line we grabbed Steve’s location as coordinates with the fn mc_location and placed them into the vars x, y, and z. Then on the next lines we used the mc_set_block fn to place some sand at the same coordinates as Steve but with some modifications. We chose the same x coordinate, a y coordinate 20 blocks higher and then successively larger z coordinates so the sand dropped in a line away from Steve.

Why don’t you take that code and start playing around with it yourself? Try adding more lines, changing the sleep times, try mixing :sand with :gravel and choose different coordinates. Just experiment and have fun!

Live Loops Unleashed

OK, it’s time to get the storm raging by unleashing the full power of the live_loop - Sonic Pi’s magical ability which unleashes the full power of live coding - changing code on-the-fly whilst it’s running!

What fun! We’re looping round pretty quickly (8 times a second) and during each loop we’re finding Steve’s location like before but then generating 3 random values:

• xd - the difference for x which will be between -10 and 10
• zd - the difference for z also between -10 and 10
• co - a cutoff value for the low pass filter between 70 and 130

We then use those random values in the fns synth and mc_set_block giving us sand falling in random locations around Steve along with a percussive rain-like sound from the :cnoise synth.

For those of you new to live loops - this is where the fun really starts with Sonic Pi. Whilst the code is running and the sand is pouring down, try changing one of the values, perhaps the sleep time to 0.25 or the :sand block type to :gravel. Now hit run again. Hey Presto! Things changed without the code stopping. This is your gateway to performing like a real VJ. Keep practising and changing things around. How different can you make the visuals without stopping the code?

Epic Block Patterns

Finally, another great way of generating interesting visuals is to generate huge patterned walls to fly towards and close by. For this effect we’ll need to move from placing the blocks randomly to placing them in an ordered manner. We can do this by nesting two sets of iteration (hit the Help button and navigate to section 5.2 of the tutorial “Iteration and Loops” for more background on iteration). The funny |xd| after the do means that xd will be set for each value of the iteration. So the first time it will be 0, then 1, then 2… etc. By nesting two lots of iteration together like this we can generate all the coordinates for a square. We can then randomly choose block types from a ring of blocks for an interesting effect:

Pretty neat. Whilst we’re having fun here, try changing bs.choose to bs.tick to move from a random pattern to a more regular one. Try changing the block types and the more adventurous of you might want to try sticking this within a live_loop so that the patterns keep changing automatically.

Now, for the VJ finale - change the two 10.times to 100.times and hit Run. Kaboom! A Huge gigantic wall of randomly placed bricks. Imagine how long it would take you to build that manually with your mouse! Double-tap space to enter fly-mode and start swooping by for some great visual effects. Don’t stop here though - use your imagination to conjure up some cool ideas and then use the coding power of Sonic Pi to make it real. When you’ve practised enough dim the lights and put on a VJ show for your friends!

Back in episode 4 of this tutorial series we took a brief look at randomisation whilst coding up some sizzling synth riffs. Given that randomisation is such an important part of my live coding DJ sets I thought it would be useful to cover the fundamentals in much greater detail. So, get your lucky hat on and let’s surf some random streams!

There is no random

The first thing to learn which might really surprise you when playing with Sonic Pi’s randomisation functions is that they’re not actually really random. What does this actually mean? Well, let’s try a couple of tests. First, imagine a number in your head between 0 and 1. Keep it there and don’t tell me. Now let me guess… was it 0.321567? No? Bah, I’m clearly no good at this. Let me have another go, but let’s ask Sonic Pi to choose a number this time. Fire up Sonic Pi v2.7+ and ask it for a random number but again don’t tell me:

Now for the reveal… was it 0.75006103515625? Yes! Ha, I can see you’re a little sceptical. Perhaps it was just a lucky guess. Let’s try again. Press the Run button again and see what we get… What? 0.75006103515625 again? This clearly can’t be random! You’re right, it’s not.

What’s going on here? The fancy computer science word here is determinism. This just means that nothing is by chance and everything is destined to be. Your version of Sonic Pi is destined to always return 0.75006103515625 in the program above. This might sound pretty useless, but let me assure you that it’s one of the most powerful parts of Sonic Pi. If you stick at it you’ll learn how to rely on the deterministic nature of Sonic Pi’s randomisation as a fundamental building block for your compositions and live coded DJ sets.

A Random Melody

When Sonic Pi boots it actually loads into memory a sequence of 441,000 pre-generated random values. When you call a random function such as rand or rrand, this random stream is used to generate your result. Each call to a random function consumes a value from this stream. Therefore the 10th call to a random function will use the 10th value from the stream. Also, every time you press the Run button, the stream is reset for that run. This is why I could predict the result to rand and why the ‘random’ melody was the same every time. Everybody’s version of Sonic Pi uses the exact same random stream which is very important when we start sharing our pieces with each other.

Let’s use this knowledge to generate a repeatable random melody:

Type this into a spare buffer and hit Run. You’ll hear a melody consisting of ‘random’ notes between 50 and 95. When it’s finished, hit Run again to hear exactly the same melody again.

Handy Randomisation Functions

Sonic Pi comes with a number of useful functions for working with the random stream. Here’s a list of some of the most useful:

• rand - Simply returns the next value in the random stream
• rrand - Returns a random value within a range
• rrand_i - Returns a random whole number within a range
• one_in - Returns true or false with the given probability
• dice - Imitates rolling a dice and returns a value between 1 and 6
• choose - Chooses a random value from a list

Check out their documentation in the Help system for detailed information and examples.

Resetting the Stream

Whilst the ability to repeat a sequence of chosen notes is essential to allow you to replay a riff on the dance floor, it might not be exactly the riff you want. Wouldn’t it be great if we could try a number of different riffs and choose the one we liked best? This is where the real magic starts.

We can manually set the stream with the fn use_random_seed. In Computer Science, a random seed is the starting point from which a new stream of random values can sprout out and blossom. Let’s try it:

Great, we get the first three notes of our random melody above: 84, 83 and 71. However, we can now change the seed to something else. How about this:

Interesting, we get 83, 71 and 61 . You might notice that the first two numbers here are the same as the last two numbers before - this isn’t a coincidence.

Remember that the random stream is just a giant list of ‘pre-rolled’ values. Using a random seed simply jumps us to a point in that list. Another way of thinking about it is to imagine a huge deck of pre-shuffled cards. Using a random seed is cutting the deck at a particular point. The fabulous part of this is that it’s precisely this ability to jump around the random stream which gives us huge power when making music.

Let’s revisit our random melody of 8 notes with this new stream resetting power, but let’s also throw in a live loop so we can experiment live whilst it’s playing:

Now, whilst it’s still playing, change the seed value from 0 to something else. Try 100, what about 999. Try your own values, experiment and play around - see which seed generates the riff you like best.

Bringing it all together

This month’s tutorial has been quite a technical dive into the workings of Sonic Pi’s randomisation functionality. Hopefully it has given you some insight into how it works and how you can start using randomisation in a reliable way to create repeatable patterns within your music. It’s important to stress that you can use repeatable randomisation anywhere you want. For example, you can randomise the amplitude of notes, the timing of the rhythm, the amount of reverb, the current synth, the mix of an FX, etc. etc. In the future we’ll take a close look at some of these applications, but for now let me leave you with a short example.

Type the following into a spare buffer, hit Run, and then start changing the seeds around, hit Run again (whilst it’s still playing) and explore the different sounds, rhythms and melodies you can make. When you find a nice one, remember the seed number so you can get back to it. Finally, when you’ve found a few seeds you like, put on a live coded performance for your friends by simply switching between your favourite seeds to create a full piece.

So far during this series we’ve focussed on triggering sounds. We’ve discovered that we can trigger the many synths built into Sonic Pi with play or synth and how to trigger pre-recorded samples with sample. We’ve also looked at how we can wrap these triggered sounds within studio FX such as reverb and distortion using the with_fx command. Combine this with Sonic Pi’s incredibly accurate timing system and you can produce a vast array of sounds, beats and riffs. However, once you’ve carefully selected a particular sound’s options and triggered it, there’s no ability to mess with it whilst it’s playing right? Wrong! Today you’re going to learn something very powerful - how to control running synths.

A Basic Sound

Let’s create a nice simple sound. Fire up Sonic Pi and in a fresh buffer type the following:

Now press the Run button at the top left to hear a lovely rumbling synth sound. Go ahead, press it again a few times to get a feel for it. OK, done? Let’s start controlling it!

Synth Nodes

A little known feature in Sonic Pi is that the fns play, synth and sample, return something called a SynthNode which represents a running sound. You can capture one of these SynthNodes using a standard variable and then control it at a later point in time. For example, let’s change the value of the cutoff: opt after 1 beat:

Let’s look at each line in turn:

Firstly we trigger the :prophet synth using the synth fn as normal. However we also capture the result in a variable called sn. We could have called this variable something completely different such as synth_node or jane - the name doesn’t matter. However, it’s important to choose a name that’s meaningful to you for your performances and for people reading your code. I chose sn as it’s a nice short mnemonic for synth node.

On line 2 we have a standard sleep command. This does nothing special - it just asks the computer to wait for 1 beat before moving onto the next line.

Line 3 is where the control fun starts. Here, we use the control fn to tell our running SynthNode to change the cutoff value to 130. If you hit the Run button, you’ll hear the :prophet synth start playing as before, but after 1 beat it will shift to sound a lot brighter.

Modulatable Options

Most of Sonic Pi’s synths and FX opts may be changed after being triggered. However, this isn’t the case for all of them. For example, the envelope opts attack:, decay:, sustain: and release: can only be set when triggering the synth. Figuring out which opts can and can’t be changed is simple - just head to the documentation for a given synth or FX and then scroll down to the individual option documentation and look for the phrases “May be changed whilst playing” or “Can not be changed once set”. For example, the documentation for the :beep synth’s attack: opt makes it clear that it’s not possible to change it:

• Default: 0
• Must be zero or greater
• Can not be changed once set
• Scaled with current BPM value

Multiple Changes

Whilst a synth is running you’re not limited to changing it only once - you’re free to change it as many times as you like. For example, we can turn our :prophet into a mini arpeggiator with the following:

In this snippet of code we just added a couple of extra things. First we defined a new variable called notes which contains the notes we’d like to cycle through (an arpeggiator is just a fancy name for something that cycles through a list of notes in order). Secondly we replaced our single call to control with an iteration calling it 16 times. In each call to control we .tick through our ring of notes which will automatically repeat once we get to the end (thanks to the fabulous power of Sonic Pi’s rings). For a bit of variety try replacing .tick with .choose and see if you can hear the difference.

Note that we can change multiple opts simultaneously. Try changing the control line to the following and listen for the difference:

Sliding

When we control a SynthNode, it responds exactly on time and instantly changes the value of the opt to the new one as if you’d pressed a button or flicked a switch requesting the change. This can sound rhythmical and percussive - especially if the opt controls an aspect of the timbre such as cutoff:. However, sometimes you don’t want the change to happen instantaneously. Instead, you might want to smoothly move from the current value to the new one as if you’d moved a slider or dial. Of course, Sonic Pi can also do this too using the _slide: opts.

Each opt that can be modified also has a special corresponding _slide: opt that allows you to specify a slide time. For example, amp: has amp_slide: and cutoff: has cutoff_slide:. These slide opts work slightly differently than all the other opts in that they tell the synth note how to behave next time they are controlled. Let’s take a look:

Notice how this example is exactly the same as before except with the addition of cutoff_slide:. This is saying that next time this synth has its cutoff: opt controlled, it will take 2 beats to slide from the current value to the new one. Therefore, when we use control you can hear the cutoff slide from 70 to 130. It creates an interesting dynamic feel to the sound. Now, try changing the cutoff_slide: time to a shorter value such as 0.5 or a longer value such as 4 to see how it changes the sound. Remember, you can slide any of the modifiable opts in exactly this way and each _slide: value can be totally different so you can have the cutoff sliding slowly, the amp sliding fast and the pan sliding somewhere in between if that’s what you’re looking to create…

Bringing it all together

Let’s look at a short example which demonstrates the power of controlling synths after they’ve been triggered. Notice that you can also slide FX just like synths although with a slightly different syntax. Check out section 7.2 of the built-in tutorial for more information on controlling FX.

Copy the code into a spare buffer and take a listen. Don’t stop there though - play around with the code. Change the slide times, change the notes, the synth, the FX and the sleep times and see if you can turn it into something completely different!

Last month in this series we took a deep technical dive into the randomisation system underpinning Sonic Pi. We explored how we can use it to deterministically add new levels of dynamic control over our code. This month we’re going to continue our technical dive and turn our attention to Sonic Pi’s unique tick system. By the end of this article you’ll be ticking your way through rhythms and riffs on your way to being a live coding DJ.

Beat Counting

When making music we often want to do a different thing depending on which beat it is. Sonic Pi has a special beat counting system called tick to give you precise control over when a beat actually occurs and even supports multiple beats with their own tempos.

Let’s have a play - to advance the beat we just need to call tick. Open up a fresh buffer, type in the following and hit Run:

This will return the current beat: 0. Notice that even if you press the Run button a few times it will always return 0. This is because each run starts a fresh beat counting from 0. However, whilst the run is still active, we can advance the beat as many times as we want:

Whenever you see the symbol #=> at the end of a line of code it means that that line will log the text on the right-hand-side. For example, puts foo #=> 0 means the code puts foo prints 0 to the log at that point in the program.

Checking the Beat

We’ve seen that tick does two things. It increments (adds one) and returns the current beat. Sometimes we just want to look at the current beat without having to increment it which we can do via look:

In this code we tick the beat up twice and then call look twice. We’ll see the following values in the log: 0, 1, 1, 1. The first two ticks returned 0, then 1 as expected, then the two looks just returned the last beat value twice which was 1.

Rings

So now we can advance the beat with tick and check the beat with look. What next? We need something to tick over. Sonic Pi uses rings for representing riffs, melodies and rhythms and the tick system has been specifically designed to work very closely with them. In fact, rings have their own dot version of tick which does two things. Firstly, it acts like a regular tick and increments the beat. Secondly it looks up the ring value using the beat as the index. Let’s take a look:

.tick is a special dot version of tick which will return the first value of the ring :a. We can grab each of the values in the ring by calling .tick multiple times:

Take a look at the log and you’ll see :a, :b, :c and then :a again. Notice that look returns 3. Calls to .tick act just like they are regular calls to tick - they increment the local beat.

A Live Loop Arpeggiator

The real power comes when you mix tick with rings and live_loops. When combined we have all the tools we need to both build and understand a simple arpegiator. We need just four things:

1. A ring containing the notes we want to loop over.
2. A means of incrementing and obtaining the beat.
3. The ability to play a note based on the current beat.
4. A loop structure to keep the arpegiator repeating.

These concepts can all be found in the following code:

Let’s look at each of these lines. First we define our ring of notes which we’ll continually play. We then create a live_loop called :arp which loops round for us. Each time round the live_loop we set our synth to :dpulse and then play the next note in our ring using .tick. Remember that this will increment our beat counter and use the latest beat value as an index into our notes ring. Finally, we wait for an eighth of a beat before looping round again.

Multiple Simultaneous Beats

A really important thing to know is that ticks are local to the live_loop. This means that each live_loop has its own independent beat counter. This is much more powerful than having a global metronome and beat. Let’s take a look at this in action:

Clashing Beats

A big cause of confusion with Sonic Pi’s tick system is when people want to tick over multiple rings in the same live_loop:

Even though each live_loop has its own independent beat counter, we’re calling .tick twice within the same live_loop. This means that the beat will be incremented twice every time round. This can produce some interesting polyrhythms but is often not what you want. There are two solutions to this problem. One option is to manually call tick at the start of the live_loop and then use .look to look up the current beat in each live_loop. The second solution is to pass a unique name to each call to .tick such as .tick(:foo). Sonic Pi will then create and track a separate beat counter for each named tick you use. That way you can work with as many beats as you need! See the section on named ticks in 9.4 of the built-in tutorial for more information.

Bringing it all together

Let’s bring all this knowledge of ticks, rings and live_loops together for a final fun example. As usual, don’t treat this as a finished piece. Start changing things and play around with it and see what you can turn it into. See you next time…

Way back in episode 3 of this Sonic Pi series we looked at how to loop, stretch and filter one of the most famous drum breaks of all time - the Amen Break. In this tutorial we’re going to take this one step further and learn how to slice it up, shuffle the slices and glue it back together in a completely new order. If that sounds a bit wild to you, don’t worry, it will all become clear and you’ll soon master a powerful new tool for your live coded sets.

Sound as Data

Before we get started let’s just take a brief moment to understand how to work with samples. By now, you’ve all hopefully played with Sonic Pi’s powerful sampler. If not, there’s no time like the present! Boot up your Raspberry Pi, launch Sonic Pi from the Programming menu, type the following into a fresh buffer and then hit the Run button to hear a pre-recorded drum beat:

A recording of a sound is simply represented as data - lots of numbers between -1 and 1 which represent the peaks and troughs of the sound wave. If we play those numbers back in order, we get the original sound. However, what’s to stop us from playing them back in a different order and creating a new sound?

How are samples actually recorded? It’s actually pretty simple once you understand the basic physics of sound. When you make a sound - for example by hitting a drum, the noise travels through the air in a similar fashion to how the surface of a lake ripples when you throw a pebble into it. When those ripples reach your ears, your eardrum moves sympathetically and converts those movements into the sound you hear. If we wish to record and play back the sound, we therefore need a way of capturing, storing and reproducing those ripples. One way is to use a microphone which acts like an eardrum and moves back and forth as the sound ripples hit it. The microphone then converts its position into a tiny electric signal which is then measured many times a second. These measurements are then represented as a series of numbers between -1 and 1.

If we were to plot a visualisation of the sound it would be a simple graph of data with time on the x axis and microphone/speaker position as a value between -1 and 1 on the y axis. You can see an example of such a graph at the top of the diagram.

Playing Part of a Sample

So, how do we code Sonic Pi to play a sample back in a different order? To answer this question we need to take a look at the start: and finish: opts for sample. These let us control the start and finish positions of our playback of the numbers which represent the sound. The values for both of these opts are represented as a number between 0 and 1 where 0 represents the start of the sample and 1 is the end. So, to play the first half of the Amen Break, we just need to specify a finish: of 0.5:

We can add in a start: value to play an even smaller section of the sample:

For fun, you can even have the finish: opt’s value be before start: and it will play the section backwards:

Re-ordering Sample Playback

Now that we know that a sample is simply a list of numbers that can be played back in any order and also how to play a specific part of a sample we can now start having fun playing a sample back in the ‘wrong’ order.

Let’s take our Amen Break and chop it up into 8 equally-sized slices and then shuffle the pieces around. Take a look at the diagram: at the top A) represents the graph of our original sample data. Chopping it into 8 slices gives us B) - notice that we’ve given each slice a different colour to help distinguish them. You can see each slice’s start and finish values at the top. Finally C) is one possible re-ordering of the slices. We can then play this back to create a new beat. Take a look at the code to do this:

1. we choose a random slice to play which should be a random number between 0 and 7 (remember that we start counting at 0). Sonic Pi has a handy function for exactly this: rand_i(8). We then store this random slice index in the variable slice_idx.
2. We define our slice_size which is 1/8 or 0.125. The slice_size is necessary for us to convert our slice_idx into a value between 0 and 1 so we can use it as our start: opt.
3. We calculate the start position s by multiplying the slice_idx by the slice_size.
4. We calculate the finish position f by adding the slice_size to the start position s.
5. We can now play the sample slice by plugging in the s and f values into the start: and finish: opts for sample.
6. Before we play the next slice we need to know how long to sleep which should be the duration of the sample slice. Luckily, Sonic Pi has us covered with sample_duration which accepts all the same opts as sample and simply returns the duration. Therefore, by passing sample_duration our start: and finish: opts, we can find out the duration of a single slice.
7. We wrap all of this code in a live_loop so that we continue to pick new random slices to play.

Bringing it all together

Let’s combine everything we’ve seen so far into a final example which demonstrates how we can take a similar approach to combine randomly sliced beats with some bass to create the start of an interesting track. Now it’s your turn - take the code below as a starting point and see if you can take it in your own direction and create something new…

In a previous episode of this Sonic Pi series we explored the power of randomisation to introduce variety, surprise and change into our live coded tracks and performances. For example, we randomly picked notes from a scale to create never-ending melodies. Today we’re going to learn a new technique which uses randomisation for rhythm - probabilistic beats!

Probability

Before we can start making new beats and synth rhythms we need to take a quick dive into the basics of probability. This might sound daunting and complicated, but really it’s just as simple as rolling a dice - honestly! When you take a regular 6 sided board game dice and roll it what’s actually happening? Well, firstly you’ll roll either a 1, 2, 3, 4, 5 or 6 with exactly the same chance of getting any of the numbers. In fact, given that it’s a 6 sided dice, on average (if you roll lots and lots of times) you’ll throw a 1 every 6 throws. This means you have a 1 in 6 chance of throwing a 1. We can emulate dice rolls in Sonic Pi with the fn dice. Let’s roll one 8 times:

Notice how the log prints values between 1 and 6 just as if we’d rolled a real dice ourselves.

Random Beats

Now imagine you had a drum and every time you were about to hit it you rolled a dice. If you rolled a 1, you hit the drum and if you rolled any other number you didn’t. You now have a probabilistic drum machine working with a probability of 1/6! Let’s hear what that sounds like:

Let’s quickly go over each line to make sure everything is very clear. First we create a new live_loop called :random_beat which will continually repeat the two lines between do and end. The first of these lines is a call to sample which will play a pre-recorded sound (the :drum_snare_hard sound in this case). However, this line has a special conditional if ending. This means that the line will only be executed if the statement on the right hand side of the if is true. The statement in this case is dice == 1. This calls our dice function which, as we have seen, returns a value between 1 and 6. We then use the equality operator == to check to see if this value is 1. If it is 1, then the statement resolves to true and our snare drum sounds, if it isn’t 1 then the statement resolves to false and the snare is skipped. The second line simply waits for 0.125 seconds before rolling the dice again.

Changing Probabilities

Those of you that have played role play games will be familiar with lots of strangely shaped dice with different ranges. For example there is the tetrahedron shaped dice which has 4 sides and even a 20 sided dice in the shape of a icosahedron. The number of sides on the dice changes the chance, or probability of rolling a 1. The fewer sides, the more likely you are to roll a 1 and the more sides the less likely. For example, with a 4 sided dice, there’s a one in 4 chance of rolling a 1 and with a 20 sided dice there’s a one in 20 chance. Luckily, Sonic Pi has the handy one_in fn for describing exactly this. Let’s play:

Start the live loop above and you’ll hear the familiar random rhythm. However, don’t stop the code running. Instead, change the 6 to a different value such as 2 or 20 and hit the Run button again. Notice that lower numbers mean the snare drum sounds more frequently and higher numbers mean the snare triggers fewer times. You’re making music with probabilities!

Combining Probabilities

Things get really exciting when you combine multiple samples being triggered with different probabilities. For example:

Again, run the code above and then start changing the probabilities to modify the rhythm. Also, try changing the samples to create an entirely new feel. For example try changing :drum_cymbal_closed to :bass_hit_c for extra bass!

Repeatable Rhythms

Next, we can use our old friend use_random_seed to reset the random stream after 8 iterations to create a regular beat. Type the following code to hear a much more regular and repeating rhythm. Once you hear the beat, try changing the seed value from 1000 to another number. Notice how different numbers generate different beats.

One thing I tend to do with this kind of structure is to remember which seeds sound good and make a note of them. That way I can easily re-create my rhythms in future practice sessions or performances.

Bringing it all together

Finally, we can throw in some random bass to give it some nice melodic content. Notice that we can also use our newly discovered probabilistic sequencing method on synths just as well as samples. Don’t leave it at that though - tweak the numbers and make your own track with the power of probabilities!

This month we’re going to take a deep dive into one of Sonic Pi’s most powerful and flexible audio FX - the :slicer. By the end of this article you will have learned how to manipulate the overall volume of parts of our live coded sound in powerful new ways. This will allow you to create new rhythmic and timbral structures and broaden your sonic possibilities.

Slice that Amp

So, what does the :slicer FX actually do? One way to think about it is that it’s just like having someone play around with the volume control on your TV or home hi-fi. Let’s take a look but first, listen to the deep growl of the following code which triggers the :prophet synth:

Now, let’s pipe it through the :slicer FX:

Hear how the slicer acts like it’s muting and unmuting the audio with a regular beat. Also, notice how the :slicer affects all the audio generated between the do/end blocks. You can control the speed at which it turns the audio on and off with the phase: opt which is short for phase duration. Its default value is 0.25 which means 4 times a second at the default BPM of 60. Let’s make it faster:

Now, play with different phase: durations yourself. Try longer and shorter values. See what happens when you choose a really short value. Also, try different synths such as :beep or :dsaw and different notes. Take a look at the following diagram to see how different phase: values change the number of amplitude changes per beat.

Phase duration is the length of time for one on/off cycle. Therefore smaller values will make the FX switch on and off much faster than larger values. Good values to start playing with are 0.125, 0.25, 0.5 and 1.

Control Waves

By default, the :slicer FX uses a square wave to manipulate the amplitude through time. This is why we hear the amplitude on for a period, then immediately off for a period, then back on again. It turns out that the square wave is just one of 4 different control waves that are supported by :slicer. The others are saw, triangle and (co)sine. Take a look at the diagram below to see what these look like. We can also hear what they sound like. For example, the following code uses (co)sine as the control wave. Hear how the sound doesn’t turn on and off abruptly but instead smoothly fades in and out:

Have a play with the different wave forms by changing the wave: opt to 0 for saw, 1 for square, 2 for triangle and 3 for sine. See how different waves sound with different phase: opts too.

Each of these waves can be inverted with the invert_wave: opt which flips it on the y axis. For example, in a single phase the saw wave typically starts high, and slowly goes down before jumping back to the top. With invert_wave: 1 it will start low and slowly go up before jumping back down again. Additionally, the control wave can be started at different points with the phase_offset: opt which should be a value between 0 and 1. By playing around with phase:, wave:, invert_wave: and phase_offset opts you can dramatically change how the amplitude is modified through time.

Setting your levels

By default, :slicer switches between amplitude values 1 (fully loud) and 0 (silent). This can be changed with the amp_min: and amp_max: opts. You can use this alongside the sine wave setting to create a simple tremolo effect:

This is just like grabbing the volume knob on your hi-fi and moving it up and down just a little so the sound ‘wobbles’ in and out.

Probabilities

One of :slicer’s powerful features is its ability to use probability to choose whether or not to turn the slicer on or off. Before the :slicer FX starts a new phase it rolls a dice and based on the result either uses the selected control wave or keeps the amplitude off. Let’s take a listen:

Hear how we now have an interesting rhythm of pulses. Try changing the probability: opt to a different value between 0 and 1. Values closer to 0 will have more space between each sound due to the likelihood of the sound being triggered being much lower.

Another thing to notice is that the probability system in the FX is just like the randomisation system accessible via fns such as rand and shuffle. They are both completely deterministic. This means that each time you hit Run you’ll hear exactly the same rhythm of pulses for a given probability. If you would like to change things around you can use the seed: opt to select a different starting seed. This works exactly the same as use_random_seed but only affects that particular FX.

Finally, you can change the ‘resting’ position of the control wave when the probability test fails from 0 to any other position with the prob_pos: opt:

Slicing Beats

One really fun thing to do is to use :slicer to chop a drum beat in and out:

This allows us to take any sample and create new rhythmical possibilities which is a lot of fun. However, one thing to be careful about is to make sure that the tempo of the sample matches the current BPM in Sonic Pi otherwise the slicing will sound totally off. For example, try swapping :loop_mika with the loop_amen sample to hear how bad this can sound when the tempos don’t align.

Changing tempo

As we have already seen, changing the default BPM with use_bpm will make all the sleep times and synth envelope durations grow or shrink to match the beat. The :slicer FX honours this too, as the phase: opt is actually measured in beats not seconds. We can therefore fix the issue with loop_amen above by changing the BPM to match the sample:

Bringing it all together

Let’s apply all these ideas into a final example that only uses the :slicer FX to create an interesting combination. Go ahead, start changing it and make it into your own piece!

In this month’s Sonic Pi tutorial we’re going to take a look at how you can start treating Sonic Pi like a real instrument. We therefore need to start thinking of code in a completely different way. Live coders think of code in a similar way to how violinists think of their bow. In fact, just like a violinist can apply various bowing techniques to create different sounds (long slow motions vs short fast hits) we will explore five of the basic live coding techniques that Sonic Pi enables. By the end of this article you’ll be able to start practicing for your own live coded performances.

1. Memorise the Shortcuts

The first tip to live coding with Sonic Pi is to start using the shortcuts. For example, instead of wasting valuable time reaching for the mouse, moving it over to the Run button and clicking, you can simply press alt and r at the same time which is much faster and keeps your fingers at the keyboard ready for the next edit. You can find out the shortcuts for the main buttons at the top by hovering the mouse over them. See section 10.2 of the built-in tutorial for the full list of shortcuts.

When performing, one fun thing to do is to add a bit of flair with your arm motion when hitting shortcuts. For example, it’s often good to communicate to the audience when you’re about to make a change - so embellish your movement when hitting alt-r just like a guitarist would do when hitting a big power chord.

2. Manually Layer your Sounds

Now you can trigger code instantly with the keyboard, you can instantly apply this skill for our second technique which is to layer your sounds manually. Instead of ‘composing’ using lots of calls to play, and sample separated by calls to sleep we will have one call to play which we will manually trigger using alt-r. Let’s try it. Type the following code into a fresh buffer:

Now, hit Run and whilst the sound is playing, modify the code in order to drop down four notes by changing it to the following:

Now, hit Run again, to hear both sounds playing at the same time. This is because Sonic Pi’s Run button doesn’t wait for any previous code to finish, but instead starts the code running at the same time. This means you can easily layer lots of sounds manually with minor or major modifications between each trigger. For example, try changing both the note: and the cutoff: opts and then re-trigger.

You can also try this technique with long abstract samples. For example:

Try starting the sample off, and then progressively halving the rate: opt between hitting Run from 1 to 0.5 to 0.25 to 0.125 and then even try some negative values such as -0.5. Layer the sounds together and see where you can take it. Finally, try adding some FX.

When performing, working with simple lines of code in this way means that an audience new to Sonic Pi has a good chance to follow what you’re doing and relate the code that they can read to the sounds they are hearing.

3. Master Live Loops

When working with more rhythmic music, it can often be hard to manually trigger everything and keep good time. Instead, it is often better to use a live_loop. This provides repetition for your code whilst also giving the ability to edit the code for the next time round the loop. They also will run at the same time as other live_loops which means you can layer them together both with each other and manual code triggers. Take a look at section 9.2 of the built-in tutorial for more information about working with live loops.

When performing, remember to make use of live_loop’s sync: opt to allow you to recover from accidental runtime mistakes which stop the live loop running due to an error. If you already have the sync: opt pointing to another valid live_loop, then you can quickly fix the error and re-run the code to re-start things without missing a beat.

4. Use the Main Mixer

One of Sonic Pi’s best kept secrets is that it has a main mixer through which all sound flows. This mixer has both a low pass filter and a high pass filter built-in, so you can easily perform global modifications to the sound. The main mixer’s functionality can be accessed via the fn set_mixer_control!. For example, whilst some code is running and making sound, enter this into a spare buffer and hit Run:

set_mixer_control! lpf: 50

After you run this code, all existing and new sounds will have a low pass filter applied to them and will therefore sound more muffled. Note that this means that the new mixer values stick until they are changed again. However, if you want, you can always reset the mixer back to its default state with reset_mixer!. Some of the currently supported opts are: pre_amp:, lpf: hpf:, and amp:. For the full list, see the built-in docs for set_mixer_control!.

Use the mixer’s *_slide opts to slide one or many opts values over time. For example, to slowly slide the mixer’s low pass filter down from the current value to 30, use the following:

You can then slide quickly back to a high value with:

When performing, it’s often useful to keep a buffer free for working with the mixer like this.

5. Practice

The most important technique for live coding is practice. The most common attribute across professional musicians of all kinds is that they practice playing with their instruments - often for many hours a day. Practice is just as important for a live coder as a guitarist. Practice allows your fingers to memorise certain patterns and common edits so you can type and work with them more fluently. Practice also gives you opportunities to explore new sounds and code constructs.

When performing, you’ll find the more practice you do, the easier it will be for you to relax into the gig. Practice will also give you a wealth of experience to draw from. This can help you understand which kinds of modifications will be interesting and also work well with the current sounds.

Bringing it all together

This month, instead of giving you a final example that combines all the things discussed, let’s part by setting down a challenge. See if you can spend a week practicing one of these ideas every day. For example, one day practice manual triggers, the next do some basic live_loop work and the following day play around with the main mixer. Then repeat. Don’t worry if things feel slow and clunky at first - just keep practicing and before you know it you’ll be live coding for a real audience.

Last month we took a look at five important techniques for mastering live coding - in other words, we explored how we could use Sonic Pi to approach code in the same way we would approach a musical instrument. One of the important concepts that we discussed was practice. This month we’re going to take a deeper dive into understanding why live coding practice is important and how you might start.

Practice regularly

The most important piece of advice is to make sure you practice regularly. As a rule I typically practice for 1-2 hours a day, but 20 mins is just fine when you’re starting out. Little but often is what you’re aiming for - so if you can only manage 10 minutes, that’s a great start.

Practice tip #1 - start to develop a practice routine. Find a nice time in the day that works for you and try and practice at that time as many days of the week as you can. Before long you’ll be looking forward to your regular session.

Learn to Touch Type

If you watch a professional musician performing on stage you’ll likely notice a few things. Firstly, when they play they don’t stare at their instrument. Their fingers, arms and bodies know which keys to press, strings to pluck or drums to hit without them having to think about it too much. This is known as “muscle memory” and although it might sound like something only professionals can do - it’s just the same as when you first learned to walk or ride a bike - practicing through repetition. Live coders use muscle memory to free their minds from having to think about where to move their fingers so they can focus on the music. This is called touch-typing - typing without having to look at the keyboard.

Practice tip #2 - learn how to touch type. There are many apps, websites and even games which can help you achieve this. Find one you like the look of and stick at it until you can code without looking down.

Code whilst standing

The body of a musician is conditioned for playing their instrument. For example, a trumpet player needs to be able to blow hard, a guitar player needs to be able to grip the fretboard with strength and a drummer needs to be able to continually hit the drums for long periods of time. So, what’s physical about live coding? Just like DJs, live coders typically perform whilst standing up and some even dance whilst they code! If you practice live coding whilst sitting at a desk and then have to get up and stand at a gig, you’ll likely find the difference very difficult and frustrating.

Practice tip #3 - stand whilst you practice. The easiest way to do this is to use a standing height desk. However, if like me you don’t have one at home, there’s a couple of low-fi options. The approach I take is to use an ironing board which happens to work rather well. Another is to stack some boxes or large books on a normal desk and place your keyboard on top of that. Also, make sure you stretch before you start practicing and try and dance a little during the session. Remember, nobody is watching you, so have fun and you’ll feel much more natural on stage.

Practice setting up

Most instruments require some assembly and tuning before they can be played. Unless you’re a rockstar with a bus full of roadies, you’ll have to set up your own instrument before your gig. This is often a stressful time and it is easy for problems to occur. One way to help with this is to incorporate the setup process into your practice sessions.

Practice tip #4 - treat setting up as an important part of your practice. For example, have a box or bag that you can keep your Raspberry Pi and keyboard in etc. Before each practice session, take out all the parts, connect everything, and work through the boot process until you have Sonic Pi running and can make sounds. Once you’ve finished practicing, take the time to carefully pack everything away afterwards. This may take some time at first, but before long you’ll be able to setup and pack everything away incredibly quickly without having to think about it.

Experiment Musically

Once you’ve set up and are ready to start making music, you might find yourself struggling to know where to start. One problem many people face is that they might have a good idea of the kinds of sounds they want to make, but are frustrated that they can’t produce them. Some people don’t even know what kind of sounds they want to make! The first thing to do is not to worry - this is very common and happens to every musician - even if they’ve been practicing for a long time. It is much more important to be making sounds you don’t like than not making any sounds at all.

Practice tip #5 - spend time making sounds and music you don’t like. Try to make time to explore new sounds and ideas. Don’t worry that it might sound terrible if it’s not the style you’re looking for. When you’re experimenting like this you increase the chance of stumbling over a sound or combination of sounds which you love! Even if 99% of the sounds you make are bad, that 1% might be the riff or intro to your new track. Forget the things you don’t like and remember the parts you do. This is even easier when you’re making music with code - just hit save!

Hear the Code

Many musicians can look at a musical score and hear the music in their head without having to play it. This is a very useful skill and it’s well worth incorporating into your live coding practice sessions. The important point is to be able to have some understanding of what the code is going to sound like. You don’t need to be able to hear it exactly in your head, but instead it’s useful to know if the code is going to be fast, slow, loud, rhythmic, melodic, random, etc. The final goal is then to be able to reverse this process - to be able to hear music in your head and know what code to write to make it. It may take you a long time to master this, but once you do, you’ll be able to improvise on stage and express your ideas fluently.

Practice tip #6 - write some code into Sonic Pi but don’t hit the Run button. Instead, try to imagine what sound it is going to produce. Then, hit Run, listen, and think about what you got right and what you didn’t. Keep repeating this until it become a natural part of your coding process. When I practice I normally have a good idea of what the code will sound like. However, I still am occasionally surprised, and then I’ll stop and spend some time thinking about why I was wrong. Each time this happens, I learn new tricks which allow me to express myself in new ways.

Remove all distractions

A common problem when practicing is to become distracted with other things. Practicing is hard and requires real discipline regardless of the kind of music you’re making - from jazz to classical to EDM. If you’re struggling to get started or make progress, it’s often too easy to hop on social media, or look something up on the internet etc. If you’ve set yourself a target of 20 minutes of practice, it’s important to try and spend all that time being as productive as possible.

Practice tip #7 - before you start practicing remove as many distractions as possible. For example, disconnect from the internet, put your phone in another room and try to practice in a quiet place where you’re unlikely to be disturbed. Try to focus on coding music and you can return to your distractions when you’ve finished.

Keep a practice diary

When you are practicing, you’ll often find your mind is full of new exciting ideas - new musical directions, new sounds to try out, new functions to write, etc. These ideas are often so interesting that you might stop what you’re doing and start working on the idea. This is another form of distraction!

Practice tip #8 - keep a practice diary by your keyboard. When you get an exciting new idea, temporarily pause your practice session, quickly jot the idea down, then forget about it and carry on practicing. You can then spend some quality time thinking about and working on your ideas after you’ve finished practicing.

Bringing it all together

Try to establish a practice routine which incorporates as many of these ideas as possible. Try to keep the sessions as fun as possible but be aware that some practice sessions will be hard and feel a little like work. However, it will all be worth it once you’ve created your first piece or given your first performance. Remember, practice is the key to success!

When people discover Sonic Pi, one of the first things they learn is how simple it is to play pre-recorded sounds using the sample function. For example, you can play an industrial drum loop, hear the sound of a choir or even listen to a vinyl scratch all via a single line of code. However, many people don’t realise that you can actually vary the speed that the sample is played back at for some powerful effects and a whole new level of control over your recorded sounds. So, fire up a copy of Sonic Pi and let’s get started stretching some samples!

Slowing Samples Down

To modify the playback rate of a sample we need to use the rate: opt:

If we specify a rate: of 1 then the sample is played back at the normal rate. If we want to play it back at half speed we simply use a rate: of 0.5:

Notice that this has two effects on the audio. Firstly the sample sounds lower in pitch and secondly it takes twice as long to play back (see the sidebar for an explanation of why this is the case). We can even choose lower and lower rates moving towards 0, so a rate: of 0.25 is a quarter speed, 0.1 is a tenth of the speed, etc. Try playing with some low rates and see if you can turn the sound into a low rumble.

Speeding Samples Up

In addition to making the sound longer and lower using a small rate, we can use higher rates to make the sound shorter and higher. Let’s play with a drum loop this time. First, take a listen to how it sounds at the default rate of 1:

Now, let’s speed it up a little:

Ha! We just moved musical genres from old-skool techno to jungle. Notice how the pitch of each drum hit is higher as well as how the whole rhythm speeds up. Now, try even higher rates and see how high and short you can make the drum loop. For example, if you use a rate of 100, the drum loop turns into a click!

Reverse Gear

Now, I’m sure many of you are thinking the same thing right now… “what if you use a negative number for the rate?”. Great question! Let’s think about this for a moment. If our rate: opt signifies the speed with which the sample is played back, 1 being normal speed, 2 being double speed, 0.5 being half speed, -1 must mean backwards! Let’s try it on a snare. First, play it back at the normal rate:

Now, play it backwards:

Of course, you can play it backwards twice as fast with a rate of -2 or backwards at half speed with a rate of -0.5. Now, play around with different negative rates and have fun. It’s particularly amusing with the :misc_burp sample!

Sample, Rate and Pitch

One of the effects of rate modification on samples is that faster rates result in the sample sounding higher in pitch and slower rates result in the sample sounding lower in pitch. Another place you may have heard this effect in every day life is when you’re cycling or driving past a beeping pedestrian crossing - as you’re heading towards the sound source the pitch is higher than when you’re moving away from the sound - the so-called Doppler effect. Why is this?

Let’s consider a simple beep which is represented by a sine wave. If we use an oscilloscope to plot a beep, we’ll see something like Figure A. If we plot a beep an octave higher, we’ll see Figure B and an octave lower will look like Figure C. Notice that the waves of higher notes are more compact and the waves of lower notes are more spread out.

A sample of a beep is nothing more than a lot of numbers (x, y, coordinates) which when plotted onto a graph will re-draw the original curves. See figure D where each circle represents a coordinate. To turn the coordinates back into audio, the computer works through each x value and sends the corresponding y value to the speakers. The trick here is that the rate at which the computer works through the x numbers does not have to be the same as the rate with which they were recorded. In other words, the space (representing an amount of time) between each circle can be stretched or compressed. So, if the computer walks through the x values faster than the original rate, it will have the effect of squashing the circles closer together which will result in a higher sounding beep. It will also make the beep shorter as we will work through all the circles faster. This is shown in Figure E.

Finally, one last thing to know is that a mathematician called Fourier proved that any sound is actually lots and lots of sine waves all combined together. Therefore, when we compress and stretch any recorded sound we’re actually stretching and compressing many sine waves all at the same time in exactly this manner.

Pitch Bending

As we’ve seen, using a faster rate will make the sound higher in pitch and a slower rate will make the sound lower in pitch. A very simple and useful trick is to know that doubling the rate actually results in the pitch being an octave higher and inversely halving the rate results in the pitch being an octave lower. This means that for melodic samples, playing it alongside itself at double/half rates actually sounds rather nice:

However, what if we just want to alter the rate such that the pitch goes up one semitone (one note up on a piano)? Sonic Pi makes this very easy via the rpitch: opt:

If you take a look at the log on the right, you’ll notice that an rpitch: of 3 actually corresponds to a rate of 1.1892 and a rpitch: of 7 corresponds to a rate of 1.4983. Finally, we can even combine rate: and rpitch: opts:

Bringing it all together

Let’s take a look at a simple piece which combines these ideas. Copy it into an empty Sonic Pi buffer, hit play, listen to it for a while and then use it as a starting point for your own piece. See how much fun it is to manipulate the playback rate of samples. As an added exercise try recording your own sounds and play around with the rate to see what wild sounds you can make.

This is the first of a short series of articles on how to use Sonic Pi for sound design. We’ll be taking a quick tour of a number of different techniques available for you to craft your own unique sound. The first technique we’ll look at is called additive synthesis. This may sound complicated - but if we expand each word slightly the meaning pops right out. Firstly, additive means a combination of things and secondly synthesis means to create sound. Additive synthesis therefore means nothing more complicated than combining existing sounds to create new ones. This synthesis technique dates back a very long time - for example, pipe organs in the middle ages had lots of slightly different sounding pipes which you could enable or disable with stops. Pulling out the stop for a given pipe ‘added it to the mix’ making the sound richer and more complex. Now, let’s see how we can pull out all the stops with Sonic Pi.

Simple Combinations

Let’s start with the most basic sound there is - the humble pure-toned sine wave:

Now, let’s see how this sounds combined with a square wave:

Notice how the two sounds combine to form a new, richer sound. Of course, we don’t have to stop there, we can add as many sounds as we need. However, we need to be careful with how many sounds we add together. Just like when we mix paints to create new colours, adding too many colours will result in a messy brown, similarly - adding too many sounds together will result in a muddy sound.

Blending

Let’s add something to make it sound a little brighter. We could use a triangle wave at an octave higher (for that high bright sound) yet only play it at amp 0.4 so it adds something extra to the sound rather than taking it over:

Now, try creating your own sounds by combining 2 or more synths at different octaves and amplitudes. Also, note that you can play around with each synth’s opts to modify each source sound before it is mixed in for even more combinations of sounds.

Detuning

So far, when combining our different synths we’ve used either the same pitch or switched octave. How might it sound if we didn’t stick to octaves but instead chose a slightly higher or lower note? Let’s try it:

If we detune our square waves by 0.7 notes we hear something that perhaps doesn’t sound in tune or correct - a ‘bad’ note. However, as we move closer to 0 it will sound less and less out of tune as the pitches of the two waves get closer and more similar. Try it for yourself! Change the detune: opt value from 0.7 to 0.5 and listen to the new sound. Try 0.2, 0.1, 0.05, 0. Each time you change the value, take a listen and see if you can hear how the sound is changing. Notice that low detune values such as 0.1 produce a really nice ‘thick’ sound, with both slightly different pitches interacting with each other in interesting, often surprising, ways.

Some of the built-in synths already include a detune option that does exactly this in one synth. Try playing with the detune: opt of :dsaw, :dpulse and :dtri.

Amplitude shaping

Another way we can finely craft our sound is to use a different envelope and options for each synth trigger. For example this will allow you to make some aspects of the sound percussive and other aspects ring out for a period of time.

In the example above I have mixed in a noisy percussive element to the sound along with some more persistent background rumbling. This was achieved firstly by using two noise synths with middling cutoff values (90 and 100) using short release times along with a noise with a longer release time but with a low cutoff value (which makes the noise less crisp and more rumbly.)

Bringing it all together

Let’s combine all these techniques to see if we can use additive synthesis to re-create a basic bell sound. I’ve broken this example into four sections. Firstly we have the ‘hit’ section which is the initial onset part of the bell sound - so uses a short envelope (e.g. a release: of around 0.1). Next we have the long ringing section in which I’m using the pure sound of the sine wave. Notice that I’m often increasing the note by roughly 12 and 24 which are the number of notes in one and two octaves. I have also thrown in a couple of low sine waves to give the sound some bass and depth. Finally, I used define to wrap my code in a function which I can then use to play a melody. Try playing your own melody and also messing around with the contents of the :bell function until you create your own fun sound to play with!

This is the second in a series of articles on how to use Sonic Pi for sound design. Last month we looked at additive synthesis which we discovered was the simple act of playing multiple sounds at the same time to make a new combined sound. For example we could combine different sounding synths or even the same synth at different pitches to build a new complex sound from simple ingredients. This month we’ll look at a new technique commonly called subtractive synthesis which is simply the act of taking an existing complex sound and removing parts of it to create something new. This is a technique which is commonly associated with the sound of analog synthesisers of the 1960s and 1970s but also with the recent renaissance of modular analog synths through popular standards such as Eurorack.

Despite this sounding like a particularly complicated and advanced technique, Sonic Pi makes it surprisingly simple and easy - so let’s dive right in.

Complex Source Signal

For a sound to work well with subtractive synthesis, it typically needs to be fairly rich and interesting. This doesn’t mean we need something hugely complex - in fact, just a standard :square or :saw wave will do:

Notice that this sound is already pretty interesting and contains many different frequencies above :e2 (the second E on a piano) which add to create the timbre. If that didn’t make much sense to you, try comparing it with the :beep:

As the :beep synth is just a sine wave, you’ll hear a much purer tone and only at :e2 and none of the high crispy/buzzy sounds which you heard in the :saw. It’s this buzziness and variation from a pure sine wave that we can play with when we use subtractive synthesis.

Filters

Once we have our raw source signal, the next step is to pass it through a filter of some kind which will modify the sound by removing or reducing parts of it. One of the most common filters used for subtractive synthesis is something called a low pass filter. This will allow all the low parts of the sound through but will reduce or remove the higher parts. Sonic Pi has a powerful yet simple to use FX system that includes a low pass filter, called :lpf. Let’s play with it:

If you listen carefully you’ll hear how some of that buzziness and crispiness has been removed. In fact, all the frequencies in the sound above note 100 have been reduced or removed and only the ones below are still present in the sound. Try changing that cutoff: point to lower notes, say 70 and then 50 and compare the sounds.

Of course, the :lpf isn’t the only filter you can use to manipulate the source signal. Another important FX is the high pass filter referred to as :hpf in Sonic Pi. This does the opposite to :lpf in that it lets the high parts of the sound through and cuts off the low parts.

Notice how this sounds much more buzzy and raspy now that all the low frequency sounds have been removed. Play around with the cutoff value - notice how lower values let more of the original bass parts of the source signal through and higher values sound increasingly tinny and quiet.

Low Pass Filter

The low pass filter is such an important part of every subtractive synthesis toolkit that it’s worth taking a deeper look at how it works. This diagram shows the same sound wave (the :prophet synth) with varying amounts of filtering. At the top, section A shows the audio wave with no filtering. Notice how the wave form is very pointy and contains lots of sharp edges. It is these hard, sharp angles that produce the high crispy/buzzy parts of the sound. Section B shows the low pass filter in action - notice how it is less pointy and more rounded than the wave form above. This means that the sound will have fewer high frequencies giving it a more mellow rounded feel. Section C shows the low pass filter with a fairly low cutoff value - this means that even more of the high frequencies have been removed from the signal resulting in an even softer, rounder wave form. Finally, notice how the size of the wave form, which represents the amplitude, decreases as we move from A to C. Subtractive synthesis works by removing parts of the signal which means that the overall amplitude is reduced as the amount of filtering that is taking place increases.

Filter Modulation

So far we’ve just produced fairly static sounds. In other words, the sound doesn’t change in any way for the entirety of its duration. Often you might want some movement in the sound to give the timbre some life. One way to achieve this is via filter modulation - changing the filter’s options through time. Luckily Sonic Pi gives you powerful tools to manipulate an FX’s opts through time. For example, you can set a slide time to each modulatable opt to specify how long it should take for the current value to linearly slide to the target value:

Let’s take a quick look at what’s going on here. Firstly we start an :lpf FX block as normal with an initial cutoff: of a low 50. However, the first line also finishes with the strange |fx| at the end. This is an optional part of the with_fx syntax which allows you to directly name and control the running FX synth. Line 2 does exactly this and controls the FX to set the cutoff_slide: opt to 3 and the new target cutoff: to be 130. The FX will now start sliding the cutoff: opt’s value from 50 to 130 over a period of 3 beats. Finally we also trigger a source signal synth so we can hear the effect of the modulated low pass filter.

Bringing it all together

This is just a very basic taster of what’s possible when you use filters to modify and change a source sound. Try playing with Sonic Pi’s many built-in FX to see what fun sounds you can design. If your sound feels too static, remember you can start modulating the options to create some movement.

Let’s finish by designing a function which will play a new sound created with subtractive synthesis. See if you can figure out what’s going on here - and for the advanced Sonic Pi readers out there - see if you can work out why I wrapped everything inside a call to at (please send answers to @samaaron on Twitter).

(This article was published in issue 9 of the Hello World Magazine)

Code is one of the most creative media that humans have created. The initially obscure symbols of parentheses and lambdas are not just deeply rooted in science and mathematics, they are the closest we have managed to get to casting the same kind of magical spells as Gandalf and Harry Potter. I believe that this provides a powerful means of engagement in our learning spaces. Through the magic of code we are able to conjure up individually meaningful stories and learning experiences.

We are surrounded by magical experiences. From the sleight of hand of a stage magician making the ball disappear into thin air, to the wonder of seeing your favourite band perform on a big stage. It is these “wow” moments that inspire us to pick up a magic book and learn the French Drop or to start jamming power chords on an old guitar. How might we create similarly deep and lasting senses of wonder that will motivate people to practice and learn the fundamentals of programming?

Musical Engines and Notation

The histories of music and computers have been intricately woven together since the inception of computing machines, or “engines” as Charles Babbage’s powerful analytical engine was called. Back in 1842 the Mathematician Ada Lovelace, who worked very closely with Babbage, saw the creative potential of these engines. Whilst these first engines had originally been designed to accurately solve hard maths problems, Ada dreamt about making music with them:

”..the engine might compose elaborate and scientific pieces of music of any degree of complexity or extent.” Ada Lovelace, 1842.

Of course, today in 2019 much of our music, regardless of genre, has either been composed, produced or mastered with a digital computer. Ada’s dream came true. It is even possible to trace the history back even further. If you see coding as the art of writing sequences of special symbols that instruct a computer to do specific things, then musical composition is a very similar practice. In Western music, the symbols are black dots positioned on a stave of lines that tell the musician which notes to play and when. Intriguingly, if we trace the roots of Western music notation back to the Italian Benedictine monk, Guido d’Arezzo, we find that the dots and lines system that modern orchestras use is just one of a number of notation systems he worked on. Some of the others were much closer to what we might now see as code.

In education, magical meaningful experiences with computers and programming languages have been explored since the late ’60s. Computer education pioneers Seymour Papert, Marvin Minsky and Cynthia Solomon explored simple Lisp-based languages that moved pens over large pieces of paper. With just a few simple commands it was possible to program the computer to draw any picture. They even experimented by extending their Logo language from drawing to music. Papert wrote about learning through experiencing the reconstruction of knowledge rather than its transmission. Getting people to play with things directly was an important part of his group’s work.

Sonic Pi Performances

Jylda and Sam Aaron perform at the Thinking Digital Conference in the Sage Gateshead. Photo credit: TyneSight Photos.

Sonic Pi has been used to perform in a wide range of venues such as school halls, nightclubs, outdoor stages at musical festivals, college chapels and prestigious music venues. For example the amazing Convo project which brought 1000 children together in the Royal Albert Hall to perform an ambitious new composition by composer Charlotte Harding. The piece was written for traditional instruments, choirs, percussion and Sonic Pi code. The pop-artist Jylda also performed with Sonic Pi in the Sage Gateshead for the Thinking Digital Conference, where she created a unique live-coded improvised remix of her song Reeled.

Sonic Pi used as one of the instruments as part of Convo at the Royal Albert Hall. Photo credit: Pete Jones.

Live coding in the classroom

Sonic Pi is a code-based music creation and performance tool that builds on all of these ideas. Unlike the majority of computing education software, it is both simple enough to use for education and also powerful enough for professionals. It has been used to perform in international music festivals, used to compose in a range of styles from classical, EDM and heavy metal, and was even reviewed in the Rolling Stone magazine. It has a diverse community of over 1.5 million live coders with a variety of backgrounds all learning and sharing their ideas and thoughts through the medium of code. It is free to download for Mac, PC and Raspberry Pi and includes a friendly tutorial that assumes you know nothing about either code or music.

Sonic Pi was initially conceived as a response to the UK’s newly released Computing curriculum in 2014. The goal was to find a motivating and fun way to teach the fundamentals of programming. It turns out that there is a lot in common and it’s huge fun to explain sequencing as melody, iteration as rhythm, conditionals as musical variety. I developed the initial designs and first iterations of the platform with Carrie Anne Philbin, who brought a teacher’s perspective to the project. Since then, Sonic Pi has undergone iterative improvements thanks to the feedback gained from observing learners and collaborating directly with educators in the classroom. A core design philosophy was to never add a feature that couldn’t be easily taught to a 10 year old child. This meant that most ideas had to be heavily refined and reworked until they were simple enough. Making things simple whilst keeping them powerful continues to be the hardest part of the project.

In order to provide the magical motivation, Sonic Pi’s design was never limited to a pure focus on education. Ideally there would be famous musicians and performers using Sonic Pi as a standard instrument alongside guitars, drums, vocals, synths, violins, etc. These performers would then act as motivational role models demonstrating the creative potential of code. For this to be possible sufficient focus and effort therefore had to be placed on making it a powerful instrument whilst still keeping it simple enough for 10 year olds to pick up. In addition to educators, I also worked directly with a variety of different artists in classrooms, art galleries, studios and venues in the early stages of Sonic Pi’s development. This provided essential feedback which enabled Sonic Pi to grow and ultimately flourish as a tool for creative expression.

There were a number of exciting and unexpected side effects of this dual focus on education and professional musicians. Many of the features are beneficial to both groups. For example, a lot of effort has been put into making error messages more friendly and useful (rather than being a huge complicated mess of jargon). This turns out to be very useful when you write a bug while performing in front of thousands of people. Additionally, functionality such as playing studio quality audio samples, adding audio effects, providing access to live audio from the microphone all turn out to make the learning experience more fun, rewarding and ultimately meaningful.

The Sonic Pi community continues to grow and share amazing code compositions, lesson plans, musical algorithms, and much more. Much of this happens on our friendly forum in_thread (in-thread.sonic-pi.net) which is home to a very diverse group of people that includes educators, musicians, programmers, artists and makers. It is a real joy to see people learn to use code to express themselves in new ways and for that in turn to inspire others to do the same.

Some fun capabilities

From a Computer Science perspective, Sonic Pi provides you with the building blocks to teach you the basics as found in the UK’s curriculum such as sequencing, iteration, conditionals, functions, data structures, algorithms, etc. However, it also builds on a number of important and relevant concepts which have become adopted in mainstream industry such as concurrency, events, pattern matching, distributed computing and determinism - all whilst keeping things simple enough to explain to a 10 year old child.

Getting started is as simple as:

A melody can be constructed with one more command, sleep:

In this example, we play the note 70 (roughly the 70th note on a piano), wait for 1 second, play note 72, wait for half a second and then play note 75. What’s interesting here is that with just two commands we have access to pretty much all of Western notation (which notes to play and when) and learners can code any melody they’ve ever heard. This leads to huge variety in expressive outcomes whilst focussing on the same computing concept: sequencing in this case.

Taking ideas from the professional music world, we can also play back any recorded sound. Sonic Pi can play any audio file on your computer but also has a number of sounds built-in to make things easy to get started:

This code will play back the drum break which was a pillarstone to early hip-hop, Drum and Bass and Jungle. For example, a number of early hip-hop artists played this drum break back at half speed to give it a more laid-back feeling:

In the 90s a number of music scenes burst out of new technology which enabled artists to take drum breaks like this apart and reassemble in a different order. For example:

In this example we introduce a basic loop called :jungle which picks a random drum hit from our audio sample, waits for an eighth of a second and then picks another drum hit. This results in an endless stream of random drum beats to dance to whilst you experience what a loop is.