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Chu-Ork-Estra: Strongly-timed, Concurrent, and On-the-fly Ork-estra


To implement a dynamically controllable set of ChucK programs for the purpose of live performance, synchronization, and orchestration of previously recorded short duration loop-able audio files. As an example of performance, human grunting sounds recorded from the home-brew microphone are used to create images of the underworld in the CCRMA 16-channel Listening Room. The grunting sounds of the audio files paint a clear image of orks marching around a desolate land working on medieval devices (similar to many scenes from the Lord of the Rings).


Thirty individual grunting sounds (Grunt.wav) (10 short, 10 medium, and 10 long) were recorded into Audacity as a single stream. The files were then cut up into isolated events and saved with a numerical naming convection. Three folders were created to organize and store each class of recorded sounds (using folder names 1,2,3) as well. The naming convection allows for easy manipulation and access within the ChucK programing language.

Once all of the files are ready, the SndBuf command in ChucK can be used to playback the files. For variation, a random number generator can be used to pick a random file among the folders and set a random playback rate (slower for lower grunts, faster for higher grunts). The playback of a single sample can then be looped and added together with other samples, all in a synchronized fashion (similar to moe.ck, larry.ck, and curly.ck files found in the ChucK distribution).

Synchronization in ChucK:

   //Define time duration
   .5::second => dur T;
   T - (now % T) => now;

For performance, quantization synchronization is only allowed on certain voices while allow others to simply loop periodically (not strongly synchronized or in phase). By varying the synchronization quantization, playback rates, tempo, volume, panning, and the number of simultaneous sample playback very interesting/exciting sounds result.

To paint the image of an underworld filled with Orks marching around, the 16-channels of discrete audio must be used intelligently with dynamic panning abilities (specific to CCRMA Listening Room). Within the listening space, four channels are spatially spaced below the listener, four above, and eight all around. The lower four channels are used for larger sounding (slower play rate) samples as in a dungeon, where as the upper four channels are used for the smaller (faster play rate) sounding samples. The middle eight channels are used for mid-range sounds. Occasionally, overlap occurs for the specific reason of sounding like an army marching around.

To simulate marching, each looping sample playback must gradually move from one speaker to the next making a circular pattern within its respective speaker range.


To do this ideally, 16 individual gain values should be used to equal-power-pan a single sample playback. Unfortunately, this requires an array of 16 gain unit-generators for a single sample playback, limiting the overall number of voices allowed in ChucK. To avoid this issue and take advantage of the simple panning requirement of moving in a circle, only two gain values can be used with a dynamically updating assignment to which channel the output audio feeds into using the chuck and unchuck commands. This allows the voices to freely move around in a circle using only two gain coefficients and reduces the panning problem to an simple equal-power panning for two channels.

Equal-power panning function in ChucK:

  fun void stereopan(Gain g[],float panvalue)
  {  //panvalue can be between [-1,1]
     panvalue/2.0+.5 => float left;
     1.0-left => float right;
     Math.sqrt(left*left + right*right) => float power;
     right/power => g[0].gain;
     left/power => g[1].gain;


Real-time input control over global parameters (master volume, tempo, rate of marching, etc) to each spork (or Ork-looping voice) can be done using reference variables as inputs to each function while using the keyboard to control the values similar to the keyboard organ.


Short Duration Grunts (zip)

Medium Duration Grunts (zip)

Long Duration Grunts (zip)