Station Point

Crafting Tune Artifacts

Fractal Wavetables

Posted on | March 20, 2009 | No Comments

floatfractBased on work by com­pos­er Ter­ran Olson, I’m releas­ing a Pro­cess­ing applet that lets you play with recursive/fractal sound syn­the­sis by set­ting a few slid­ers.

Background

Inspired by an arti­cle on CDM, and Ter­ran Olson’s work in par­tic­u­lar, I dug into cre­at­ing a slight­ly more gen­er­al ver­sion of frac­tal set syn­the­sis.

In essence, you use a bank of slid­ers to give the pro­gram a wavetable “seed”, which is imme­di­ate­ly sub­di­vid­ed into sound — each sam­ple is replaced by a copy of the wavetable, mul­ti­plied by the old sam­ple val­ue, and so on.…

This recur­sion con­tin­ues until the desired length of audio data has been gen­er­at­ed. The ini­tial val­ue always begins at “1″.  For a seed of “1 0.5 1″, you get the fol­low­ing as the first three steps:

1 =>
1 0.5 1 =>
1 0.5 1 0.5 0.25 0.5 1 0.5 1 =>
1 0.5 1 0.5 0.25 0.5 1 0.5 1 0.5 0.25 0.5 0.25 0.125 0.25 0.5 0.25 0.5 1 0.5 1 0.5 0.25 0.5 1 0.5 1 => …

Try it

Click the thumb­nail below to run the applet in your brows­er (requires Java):

fractalwavetables2-300x233

Or get the down­load­able appli­ca­tion ver­sion here (so you can save out audio files):
Mac OS X ver­sion
Win­dows ver­sion
Lin­ux ver­sion

If you’re curi­ous about how this was writ­ten, the pub­lic git repos­i­to­ry for this project lives at:
http://wiki.github.com/jdnorthrup/fractalwavetablesketch

Thoughts

Ini­tial­ly, I found the whole idea that the music can be self-sim­i­lar from the wave­form lev­el, up to the “LFO” lev­el, up to the rhyth­mic phrase, to the over­all flow of a pas­sage of sound — rather mind-expand­ing.

Inter­est­ing­ly, the sounds pro­duced from this can sound spec­tac­u­lar through deep reverbs and oth­er pro­cess­ing. They’re almost the same ampli­tude at all fre­quen­cies in their range, quite unlike nat­ur­al har­mon­ic spec­tra. Try run­ning a steep res­o­nant band­pass across some of the more com­plex sounds.

If you do any­thing cool with this app, please send me a link!

Sonograph of a fractal sound generated using this method.

Sono­graph of a frac­tal sound.

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