stop(timeFromNow) {
    var t = timeFromNow || 0;
    var now = p5sound.audiocontext.currentTime;
    if (this.isPlaying) {
      this.clock.stop(now + t);
      this.isPlaying = false;
    }
  }
Stop the loop
@method  stop
@for p5.SoundLoop
@param  {Number} [timeFromNow] schedule a stopping time