loop(time) {
    this.looping = true;
    // rest onended function
    this.onended = function () {
      this.partStep = 0;
    };
    var t = time || 0;
    this.start(t);
  }
Loop playback of this part. It will begin
 looping through all of its phrases at a speed
 determined by setBPM.

 @method  loop
 @for p5.Part
 @param  {Number} [time] seconds from now