function dsp(t) {

  var tmod = t - Math.floor( t ); // basically, remove the whole-number portion of t, so 3.3 becomes 0.3, 7.87 becomes 0.87, etc.

  /**
   * Sine pattern:
   * - 220 Hz for a quarter-second
   * - silence for a quarter-second
   * - 254 Hz for a quarter-second
   * - silence for a quarter-second
   */

  var melody = 0;

  if ( tmod < 0.25 ) {
    melody = sinewave( t, 220 );
  } else if ( tmod >= 0.5 && tmod < 0.75 ) {
    melody = sinewave( t, 254 );
  }

  /**
   * Noise pattern:
   * - on for an eighth-second
   * - off for an eighth-second
   * - repeat
   */

  var noise = 0;

  if (
    tmod < 1/8 ||
    ( tmod >= 2/8 && tmod < 3/8 ) ||
    ( tmod >= 4/8 && tmod < 5/8 ) ||
    ( tmod > 6/8 && tmod < 7/8 )
  ) {
    noise = Noise();
  }

  return 0.5 * melody + 0.2 * noise;

}

function sinewave( t, freq ) {
  return Math.sin(2 * Math.PI * t * freq );
}

function Noise() {
  return Math.random() * 3 - 1; // return a random number between -1 and 1
}