Music Tech Workshop

Open Sound Control (OSC)
& SuperCollider

by Antoine (@notkaramel)

Sections

Why use OSC? What is SuperCollider

Prerequisite knowledge

It is recommended that you have some background knowledge on

• Object Oriented Programming (OOP)
• Signal processing
• The client-server architecture
• Network protocol (UDP, HTTP, TCP)

Links

Project Source Code:

What is Open Sound Control?

Why use OSC?

Why not use MIDI???

What is SuperCollider?

"What is Open Sound Control?"

"Why use OSC?"
"Why not use MIDI?"

MIDI is a protocol standard made for hardware synthesizer with electrical circuit limitations. Meanwhile, OSC travels through the internet via UDP (or User Datagram Protocol).

"What is SuperCollider?"

We will use a program called SuperCollier to use and interact directly with OSC and create an application using it.

Let's make a Hello World program.

                        
        "Hello World!".postln;
                        
                    

---

You should get this on the post window.

Documentation

SuperCollider has a very extensive documentation.
You can access it by pressing Ctrl Shift D or Cmd Shift D

Documentation

You can also access the documentation of a function by Ctrl D or Cmd D with the cursor on the code.

Documentation

You can play with the example codes on the documentation with Ctrl Enter or Cmd Enter

Step 3: SC Basics

Let's start with making a sinusoid wave!

3.1. Create a SinOsc object with the params:

You can always check the documentation:

3.1. Create a SinOsc object with the params:

Note: Unspecified parameter(s) will use the default value(s)!!

3.2. Wrap the oscillator with curly brackets.
You now have a Function

3.3. You can add .play to play the Function to make it play the sound!

3.4. Press Ctrl Enter or Cmd Enter with the cursor on the line to play the sine wave

It's a pure A4 signal!

3.5. Press Ctrl . or Cmd . to stop the audio playing

3.6. Variables

~myThing = ...
or 

var myThingy2 = ...
            

Step 4

---

Synth & SynthDef

Remember OOP?

SynthDef

    // Create a new Synth Definition
    SynthDef.new(\name, {Function});

    // Add (Sending) the SynthDef to the server
    SynthDef.new(\name, {Function}).add;
                        

SynthDef - Example

    // Create a new Synth Definition
    SynthDef.new(\Sinusoid, {
        var freq = 440; // A4
        var sinFunc = SinOsc.ar(freq);
        Out.ar(0, sinFunc);
    }).add;

                        

We will learn about Out function soon!

SynthDef - Example

(
    // Create a new Synth Definition
    SynthDef.new(\Sinusoid, {
        var freq = 440; // A4
        var sinFunc = SinOsc.ar(freq);
        Out.ar(0, sinFunc);
    }).add;
)

                        

Synth - Example

    x = Synth(\Sinusoid);

// free the UGen when you're done
x.free; // or `Ctrl .` / `Cmd .` 
    
                        

SynthDef - Arguments

(
    // Create a new Synth Definition
    SynthDef.new(\Sinusoid, {
        arg freq = 440; // A4
        var sinFunc = SinOsc.ar(freq)
        Out.ar(0, sinFunc);
    }).add;
)

                        

SynthDef - Arguments

(
    // Create a new Synth Definition
    SynthDef.new(\Sinusoid, {
        | freq = 440 | // A4
        var sinFunc = SinOsc.ar(freq)
        Out.ar(0, sinFunc);
    }).add;
)

                        

Synth - with Arguments

    x = Synth(\Sinusoid, [\freq, 400]);
x.set(\freq, 600);

// Having multiple arguments?
x = Synth(\OtherSinusoid, [\freq, 400, \amp, 0.4]);
                        

Step 5

---

Signal Processing Basics

5.1. Basic functions

\[\begin{aligned} & \text{Sine Wave: } x(t) = A\sin(2\pi ft + \phi) \\ & \text{Pulse Train: } x(t) = \sum_{n=-\infty}^{\infty} A\cdot \text{rect}\left(\frac{t-nT}{T_p}\right) \\ & \text{Saw Tooth: } x(t) = \frac{A}{T}t - \left\lfloor \frac{A}{T}t \right\rfloor \\ \end{aligned} \]

How can you implement those in SuperCollider??

5.1. Basic functions

in SuperCollider

\[\begin{aligned} & \text{Sine Wave: } x = SinOsc.ar(f,\phi,Amp) \\ & \text{Pulse Train: } x = Pulse.ar(f, width, Amp) \\ & \text{Saw Tooth: } x = Saw.ar(f,Amp) \\ \end{aligned} \]

5.2. Signal Manipulation

Amplitude Modulation (AM)

Frequency Modulation (FM)

5.2. Signal Manipulation

Additive & Subtractive Synthesis

{
    var freq = 400, amp = 1;
    SinOsc.ar(freq, 0, amp)
    + SinOsc.ar(freq*2, 0, amp/2)
    + SinOsc.ar(freq*4, 0, amp/4)
}.play;

                        

5.3. Scopes

SuperCollider has built-in scopes to help us visualize our signals

// s is the server variable.
// Here we want to use the time scope
s.scope;

// There is also a Spectrum Analyzer
FreqScope.new(width: 522, height: 300, busNum: 0,
            scopeColor, bgColor, server)

// Create a FreqScope for Bus 0 on our current server, 500x400
FreqScope(500, 400, 0, s);

                    

Step 6

---

Let's make a note!

with Envelope 💌

Envelope function: Env

In essence, an envelope is a function that changes the amplitude of a sound over time. It puts the sound in an "envelope" of sorts, hence the name.

There are many ways to create an envelope in SuperCollider.

Envelope function: Env

Env.new(
    levels: [0, 1, 0.9, 0],
    times: [0.1, 0.5, 1],
    curve: 'lin'
).plot;

Using Envelope function: EnvGen

The EnvGen function is used to generate an envelope.

You can think Env is the blueprint or specifications of the envelope, while EnvGen is the instance that you can use.

Env example

~envFunc = Env.perc(0.1, 0.7);

This is also called an Attack-Release envelope

Types of envelope

For more types of envelope, you can check the
SuperCollider documentation.

Additionally, you can checkout the basics and types of envelope at https://thewolfsound.com/envelopes/

Types of envelope: ADSR

ADSR is the most common type of envelope,
commonly seen in a lot of digital audio workstation (DAW)

Using Envelope function: EnvGen

EnvGen.ar(
    envelope,
    gate: 1.0,
    levelScale: 1.0,
    levelBias: 0.0,
    timeScale: 1.0,
    doneAction: 0
);
                    

For the scope of this workshop, we will only look into the envelope function and the doneAction parameter.

doneAction parameter

This parameter tells the server what to do when the envelope is done.

EnvGen example

~envFunc = Env.perc(0.1, 0.7);
EnvGen.kr(~envFunc, doneAction: Done.freeSelf);
                    

Making a note

(
{
    ~envFunc = Env.perc(0.1, 0.7);
    ~env = EnvGen.kr(~envFunc, doneAction: Done.freeSelf);
    SinOsc.ar(440) * ~env;
}.play
)

Step 7

Output channels & Panning

Spatialized Audio!? 🎧

Channel / Bus

Generally, most generic computers has two output channels:
the left channel (Bus 0) &
the right channel (Bus 1).

 // to see the channels
s.meter

// Output a synth
Out.ar(bus:0, mySynth);
Out.ar(bus:1, mySynth);
                    

Why do we need the Out function?

Out function

The Out function is used to output the sound to a specific channel.

Out.ar(bus:0, mySynth);

This is particularly useful for multi-speaker setup!

Multichannel Expansion

We can create a function with multiple audio channels by using the array syntax.

// one channel
{ Blip.ar(800,4,0.1) }.play;

// two channels in an array
{ [ Blip.ar(800,4,0.1), WhiteNoise.ar(0.1) ] }.play;

// two frequencies in an array
{ SinOsc.ar([440, 880], 0, 0.2) }.play;

                    

Multichannel Expansion + Out

We can make the Out function output to multiple channels using multichannel expansion.

(
{
    ~sound1 = Blip.ar(800,4,0.1);
    ~sound2 = WhiteNoise.ar(0.1);
    // the explicit way
    Out.ar([0,1], [~sound1, ~sound2]);

    // using multichannel expansion
    Out.ar(0, [~sound1, ~sound2]);
}.play;
)
                    

Multichannel Expansion + Out

// using multichannel expansion
Out.ar(0, [~sound1, ~sound2]);

          

All sounds are expanded from channel 0 to the next channels.

What if you have more sound functions than channels?

The sound(s) on unavailable channel(s) will not be played!

The Pan2 function

Pan2.ar(in, pos: 0.0, level: 1.0)

where in is the output sound,
pos is the relative position to the center
(-1 is left, +1 is right)

A complete example

// Making a note
(
SynthDef(\MyNote, { | freq = 440, amp = 0.5 |
    // Create a wave
    ~wave = SinOsc.ar(freq, 1, amp);

    // Envelope the sound
    ~envFunc = Env.perc(0.1, 0.7);
    ~env = EnvGen.kr(~envFunc, doneAction: Done.freeSelf);

    ~sound = ~wave * ~env;

    // Equally panned on both channels
    Out.ar(0, Pan2.ar(~sound, 0));
}).add
)

Synth("MyNote")

[tangent] Spatialized Audio

To achieve spatialized audio, we need more than just panning with Pan2.

Ambisonics is a technique to achieve spatialized audio.
It uses concepts such as W, X, Y, Z to represent the sound in a 3D space.

[tangent] Spatialized Audio

Head-related transfer function (HRTF) is another technique to achieve spatialized audio.

Step 8

OSC message & scsynth Server

Brace yourself!

The client-server architecture

How can you interact with the server?

How can you encode an OSC message?

What can you do with all of these knowledge?

The scsynth server

The scsynth server is the server that runs the SuperCollider synthesis engine.

Interact with the scsynth server

// Boot the server
s.boot;

// Show the server address & port
s.addr;

// Quit the server
s.quit;

// Show the server output scope (time vs amplitude)
s.scope;

// Show the server input & output meter
s.meter;

OSC encoding schema

OSC follows a schema as follows:

On the SuperCollider IDE

The IDE provides client-side code that allows user to send OSC messages

~mySine = SynthDef("sine", {...}).add;

// is equivalent to
~mySine = SynthDef("sine", {...});
~mySine.send(s);

// write SynthDef to disk. .send(s) doesn't write to disk
~mySine = SynthDef("sine", {...}).load(s);
                            
                        

On the SuperCollider IDE

To play a Synth:

// play a Synth "\sine" with "freq" augument 900
// x is used to keep track of the node number
s.sendMsg("/s_new", "sine",
        x = s.nextNodeID, 1, 1, "freq", 900);

// to change the frequency of the Synth
s.sendMsg("/n_set", x, "freq", 400);

// to free the node
s.sendMsg("/n_free", x);
                    

Usage of OSC outside of SuperCollider

OSC allows you to control the synthesizer server from a different program, or even a different machine!

We will use python-osc for our game later!

Step 9

Extras

Just a brief introduction to the endless possibility
you can do with SuperCollider.

sclang

sclang is the SuperCollider language interpreter. It behaves similarly to Python.

sclang mysynth.scd

Load different SuperCollider files

You can also load multiple different files with SynthDefs.

"mySynth1.scd".load;
"mySynth2.scd".load;

Loop, repeat, & Routine

You can set up repeated tasks in SuperCollider using a n.do(), a Routine, .loop, or .repeat() methods.

20.do({ |i|
    i.postln; // print all numbers from 0 to 19
});


[1, 5, 3].do({ |i|
	i.postln;  // print out 1, 5, 3
});


t = Task({ { "Yippee".postln; 1.wait; }.loop});
t.start;
t.stop;

                

wait

You can set up a time pause between events or tasks using the .wait method inside a Task or a Routine.

wait

t = Task({
    {
        "Yippee".postln;
        1.wait; // wait for 1 second
    }.loop});
t.start;
t.stop;

x = Routine(
	10.do({
		"Howdy".postln;
		1.wait; // wait for 1 second
    });
)

x.play();
                

MIDI

SuperCollider can also interact with MIDI devices, uses MIDI standards, etc.

~E4midi = 64.midicps; // convert MIDI note to frequency

// Example: Play a MIDI note 
{ SinOsc.ar(64.midicps); }.play(); 

MIDIClient.init; // Start the MIDI client
MIDIIn
MIDIOut
MIDIFunc

                

Application

Let's make a game!

Play the game

Make sure you have a running SuperCollider server at localhost:57110.

(.venv) python game.py

Use arrow keys to move the running blobby.
Press Space to spin.

Thank you for attending the workshop!

🎉 🎉 🎉

Any questions?

Curious to learn more about SuperCollider?