Infinitely Descending Chord

infinitely.js

/**
 * INFINITELY DESCENDING CHORD PROGRESSION (v1.1)
 *
 * Enjoy this chord progression that loops forever....
 * By Thai Pangsakulyanont (https://github.com/dtinth)
 *
 * https://gist.github.com/dtinth/11371713
 */

var step = 0.1
var ss = 0.1
var sequence = [0, 3, 8, 3]
var sequence2 = [12, 12, 12, 7, 7, 7, 7, 7, 12, 12, 12, 10, 10, 10, 9, 9] 

return function (t) {
  return melody(t) * 0.7 + melody(t - 0.5) * 0.2 + melody2(t) * 0.4 + kick(t) * 0.8
}

function kick(t) {
  var ts = t % (4 * ss)
  return Math.sin(60 * (1 - Math.exp(-ts * 30))) * Math.exp(-ts * 20)
}

function melody(t) {
  var step = (t / ss)
  var i = (step % 4) | 0
  var dec = (step / 16) | 0
  return synth(ssaw, t, 64, sequence[i] - dec + (dec % 2 != 0 && i > 0 ? 1 : 0)) * 0.7 +
    synth(sin, t, 40, -dec) * 0.7 * (i > 1 ? 1 : 0)
}

function melody2(t) {
  var step = (t / ss / 2)
  var i = (step % 16) | 0
  var dec = ((step / 16) | 0) * 2
  return synth(triangle, t, 48, sequence2[i] - dec)
}
function sin(t, f) {
  return Math.sin(t * Math.PI * 2 * f)
}
function saw(t, f) {
  return (t * f) % 1 * 2 - 1
}
function ssaw(t, f) {
  return saw(t, f) * 0.4 + saw(t, f * 0.99) * 0.3 + saw(t, f / 0.99) * 0.3
}
function triangle(t, f) {
  return Math.abs(1 - (2 * t * f) % 2) * 2 - 1
}
function synth(f, t, b, c) {
  var tone = ((c % 12) + 12) % 12
  var q = (tone / 12)
  var freq = mtof(b + tone)
  return f(t, freq) * q + f(t, freq * 2) * (1 - q)
}

function mtof(c) {
  return  440 * Math.pow(2, (c - 69) / 12)
}