JSONloops.js

/*******************************
JSONloops is a javascript audio sequencer that runs on JSON arrays of sounds

    JSONloops are nested arrays that contain: a nested array, a sound, or null
    
    the arrays are nested in the following hierarchy 
    
    * SONG
    *   TRACKS
    *     MEASURES
    *       BEATS

    a 2 measure song with 4 beats in each measure might be structured as something like this
    
    * SONG
    *   TRACK1
    *     MEASURE1
    *       BEAT
    *       BEAT
    *       BEAT
    *       BEAT            
    *     MEASURE2
    *       BEAT
    *       BEAT
    *       BEAT
    *       BEAT            
    *   TRACK2
    *     MEASURE1
    *       BEAT
    *       BEAT
    *       BEAT
    *       BEAT            
    *     MEASURE2
    *       BEAT
    *       BEAT
    *       BEAT
    *       BEAT            
    *   TRACK3
    *     MEASURE1
    *       BEAT
    *       BEAT
    *       BEAT
    *       BEAT            
    *     MEASURE2
    *       BEAT
    *       BEAT
    *       BEAT
    *       BEAT            
  
  *******************************/

var sys = require('sys');
var play = require('./lib/play');

// measures in song
var measures = 1;
// beats per measure
var beats = 4;
// beats per minute
var bpm = 60;

// the current beat position
var position = 0;

// simple drum kit
var drums = {
  kick : './wavs/kick.wav',
  snare : './wavs/snare.wav',
  tick : './wavs/tick.wav'
};

// simple 4 beat drum loop, notice the empty arrays which represent beats with no note playing
var song = [
  [[[drums.kick], [],[drums.kick], [drums.kick]],[[drums.kick], [],[drums.kick], [drums.kick]]],
  [[[],[],[],[]],[[],[],[],[]]],
  [[[drums.tick],[drums.tick],[drums.tick],[drums.tick]],[[drums.tick],[drums.tick],[drums.tick],[drums.tick]]]
];

var theMix = [];
function json_loop( song ){

    // for every measure in the song
    for(var m = 0; m < measures; m++){
      // for every measure in track
      for(var b = 0; b < beats; b++){
        // for every track in the song
        for(var t = 0; t < song.length; t++){
          //play.start(song[t][m][b]);
          theMix.push(song[t][m][b]);
          //sys.puts(JSON.stringify(song[t][m][b]));
        }
      }
    }
}


function step(steps){
  if(!steps.length){
    json_loop(song);
    step(theMix);
    return;
  }
  setTimeout(function(){
    // calculate the node we are going to pull and play now
    for(var b = 0; b < beats; b++){
      play.start(steps.pop());
    }
    step(steps);
  },60000 / bpm);
}

json_loop(song);
step(theMix);
sys.puts(JSON.stringify(theMix));