probabilistic web audio drum machine

drums.js

var samples = {
  kick: new Wad({source: '/samples/kick.wav'}),
  chh: new Wad({source: '/samples/chh.wav'}),
  snare: new Wad({source: '/samples/snare.wav'}),
  ohh: new Wad({source: '/samples/ohh.wav'}),
  cym: new Wad({source: '/samples/cym.wav'}),
  shkr: new Wad({source: '/samples/shkr.wav'}),
  ltom: new Wad({source: '/samples/ltom.wav'}),
  mtom: new Wad({source: '/samples/mtom.wav'}),
  htom: new Wad({source: '/samples/htom.wav'}),
  clap: new Wad({source: '/samples/clap.wav'})
};

var drums = {
  kick: [1, 0.3, 0.3, 0.1, 1, 0.3, 0.3, 0.1, 1, 0.3, 0.3, 0.1, 1, 0.3, 0.5, 0.3],
  chh: [0.5, 0.5, 0.3, 0.5, 0.5, 0.5, 0.3, 0.5, 0.5, 0.5, 0.3, 0.5, 0.5, 0.5, 0.3, 0.5],
  snare: [0.1, 0.1, 0.3, 0.1, 0.7, 0.1, 0.3, 0.1, 0.1, 0.1, 0.3, 0.1, 0.7, 0.1, 0.3, 0.1],
  ohh: [0.1, 0.1, 0.5, 0.1, 0.1, 0.1, 0.5, 0.1, 0.1, 0.1, 0.5, 0.1, 0.1, 0.1, 0.5, 0.1],
  cym: [0.3, 0.1, 0.2, 0.1, 0.1, 0.1, 0.3, 0.1, 0.2, 0.1, 0.3, 0.1, 0.3, 0.3, 0.3, 0.3],
  shkr: [0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3, 0.3],
  ltom: [0.2, 0.2, 0.1, 0.1, 0.2, 0.2, 0.1, 0.1, 0.3, 0.2, 0.1, 0.1, 0.3, 0.5, 0.3, 0.1],
  mtom: [0.1, 0.1, 0.2, 0.2, 0.1, 0.2, 0.1, 0.2, 0.1, 0.3, 0.2, 0.3, 0.5, 0.3, 0.1, 0.1],
  htom: [0.1, 0.2, 0.2, 0.1, 0.2, 0.1, 0.2, 0.1, 0.2, 0.1, 0.3, 0.2, 0.3, 0.3, 0.5, 0.3],
  clap: [0.1, 0.1, 0.3, 0.1, 0.5, 0.1, 0.3, 0.1, 0.1, 0.1, 0.3, 0.1, 0.5, 0.1, 0.3, 0.1]
};

var bpm = 140;
var intervalTime = 60000.0 / bpm;
var position = 0;

window.setInterval(function(){
  for(var drum in drums){
    if(Math.random() < drums[drum][position]){
      samples[drum].play();
    }
  }
  position++;
  if(position >= 16) position = 0;
}, intervalTime);

gistfile1.txt

uses WAD to load and play samples cuz I aint about to touch an audio context. https://github.com/rserota/wad

on each beat, the computer iterates over the drums, generates a random number, compares it to that drums probability for that beat, and plays the drum if it matches.

TODO:
teach computer how to generate new probabilities, perhaps by markov chaining MIDI files, or by hand writing a bunch and setting an algorithm loose on them.

figure out how to generate sick acid bass lines