amp(vol, rampTime = 0, tFromNow = 0) {
    const now = p5sound.audiocontext.currentTime;
    const startTime = now + tFromNow;
    const endTime = startTime + rampTime + 0.001;
    const currentVol = this.output.gain.value;
    this.output.gain.cancelScheduledValues(now);
    this.output.gain.linearRampToValueAtTime(currentVol, startTime + 0.001);
    this.output.gain.linearRampToValueAtTime(vol, endTime);
  }
Set the output volume of the filter.

 @method  amp
 @for p5.Effect
 @param {Number} [vol] amplitude between 0 and 1.0
 @param {Number} [rampTime] create a fade that lasts until rampTime
 @param {Number} [tFromNow] schedule this event to happen in tFromNow seconds