stop(timeFromNow) {
    var time = timeFromNow || 0;

    if (this.mode === 'sustain' || this.mode === 'untildone') {
      this.stopAll(time);
      this._playing = false;
      this.pauseTime = 0;
      this._paused = false;
    } else if (this.buffer && this.bufferSourceNode) {
      var now = p5sound.audiocontext.currentTime;
      this.pauseTime = 0;
      this.bufferSourceNode.stop(now + time);
      this._counterNode.stop(now + time);
      this._playing = false;
      this._paused = false;
    }
  }
Stop soundfile playback.

@method stop
@for p5.SoundFile
@param {Number} [startTime] (optional) schedule event to occur
                            in seconds from now