Supercollision of the Week, #1

I’m going to post one new track a week, as a way of learning how to use SuperCollider effectively. The tracks themselves will be hosted on Soundcloud and I will write a short post about each one here explaining some of the techniques that went into them.

This track was partially inspired by James Harkins‘ excellent Patterns tutorial [pdf], which you should go read right now if you haven’t already. In fact, I’d recommend printing it out and having it with you at all times. Briefly, patterns are an extremely powerful method for generating streams of values in SuperCollider. These values can control anything: pitch, loudness, duration, sample offset, etc. Using Pbind, several values can be combined into an event stream, like so:

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Pbind(\freq, 2640+Pwhite(-10,10,inf),
\delta, Pseq([0.75, 0.75, 0.75, 0.5, 0.25], inf),
\sustain, 0.0625,
\amp, Pgbrown(0.2,0.4, 0.02, inf),
\instrument, Prand([\sawpass, \singrain],inf))

In this example, the frequency is 2640 Hz plus a random number between -10 and 10 Hz. The time between notes (delta) is the five-element sequence in brackets. The sustain is always 0.0625s, for a short, percussive sound. The loudness (\amp) is controlled by Pgbrown which generates geometric Brownian motion, in this case with a low of 0.2, a high of 0.4, and a step size of 0.002. Finally, the Synth to use is randomly chosen every note, and can be either \sawpass or \singrain.

There is a large library of pre-existing patterns, but if what you need doesn’t exist, the Prout class lets you make any routine into a pattern.

In this week’s track, I implemented a very simple Markov chain using a Prout. Overall, there are four Pbinds playing simultaneously. The four Pbinds go into a simple mixer that I made, about which more in a later post. I also made a simple PlayBuf-based Synth that loops two seconds of a sample, with the start position given by the x-position of the mouse (s/o to friends who send you field recordings from their travels).

The code is structured into two files: Setup.scd, which boots the server, creates all the SynthDefs, sets up the signal routing, and draws the GUI; and Patterns.scd, which specifies the patterns for each Pbind. I use Pbindef, which allows you to create a global dictionary of patterns which can then be modified on the fly. The piece is in just intonation (duh) with a base frequency of 82.5 Hz.

Code is below.