blogInProcess

Post objective is to recycle our first patch to explore granulation techniques. To granulate means to segment a sound signal into tiny grains (Roads 2001).

We want to granulate from a sound file, to do it we need to load a sound file into a buffer:

m = Buffer.read(s, "sounds/a11wlk01.wav");

We’re going to set a synth definition:

SynthDef("grain", {arg pan=0.0, rate=1, startPos=0.0, amp=1, dur=0.05; 
 
	var env = EnvGen.kr(Env.sine(dur, 1), 1.0, doneAction: 2);
	var synth = PlayBuf.ar(1,buffer, rate, 1, startPos, 0)*env;
 
	Out.ar(0,Pan2.ar(synth*amp, pan))
}).send(s);

This synth is based on SC3 PlayBuf UGen. PLayBuf plays a sample from a buffer. Pay  attention to startPos parameter: it defines the sample frame to start playback.

We can test our synth evaluating the next sencency:

Synth("grain");

Now we are going to make a loop that plays sample segments. We use random numbers to set the composition parameters.

Task({
    var rate, time, dur, startPos;
 
    loop{
        dur = rrand(0.1, 0.3);
        rate = rrand(0.7, 1.1);
        time = exprand(0.1, 2.0);
 
        startPos = rrand(0, m.numFrames);
 
        Synth("grain", [\dur, dur, \rate, rate, \startPos, startPos, \amp, 1]);
        time.wait;
    };
}).play;

I want to open my blog showing a brief introduction to random techniques in music (or simply sound) composition. The example algorithms are going to be implemented in SC3 sound programing environment.

Firstly we need to define a Synth:

SynthDef("grain", { arg dur, frq;
	var env = EnvGen.kr(Env.sine(dur, 1), 1.0, doneAction:2);
 	var synth = SinOsc.ar(frq)*env;
 
 	Out.ar(0, Pan2.ar(synth, 0))
}).send(s);

This synth makes a sine wave with a sine envelop. We only need two parameters to get sound with this synth: frequency and duration of the sound. We can test our synth named “grain” evaluating the next sentence in SC3:

Synth("grain", [\dur, 1, \frq, 400]);

After evaluate this sentence we get a sound of 400Hz with one second duration.

We are going to make a loop now! We can get a series of sine waves with the next piece of code:

Task({
	var dur = 1;
	var frq = 400;
	var time = 1;
 
	loop{
		Synth("grain", [\dur, dur, \frq, frq]);
		time.wait;
	};
}).play;

We can see that we have three new variables: dur, frq and time; the first two are the synth parameters and the third (time) is used to define the time between the start of a sound and the start of the next sound. We can think about these three variables as a parameters of the sound composition.

Now we are going to use a random number generator to get different values for our compositional parameters in each iteration:

Task({
	var frq;
	var time;
	var dur;
 
	loop{
		dur = rrand(0.1, 0.3);
		frq = rrand(300, 1000);
		time = rrand(0.3, 1.0);
 
		Synth("grain", [\dur, dur, \frq, frq]);
		time.wait;
	};
}).play;

The rrand(a, b) SC3 function is used to generate random numbers between the parameters a and b.

Just we have seen a simply way to generate some series of sine waves, what can we do now?

• replace rrand() with other random number generators like exprand()
• add to your SynthDef more parameters like amplitude or panning

Donwload Example Code