triggerRelease(secondsFromNow = 0) {
    this.env.ramp(this.output.gain, secondsFromNow, 0);
  }
Trigger the release of the Envelope. This is similar to releasing
 the key on a piano and letting the sound fade according to the
 release level and release time.

 @param  {Number} secondsFromNow time to trigger the release
 @method  triggerRelease
 @for p5.MonoSynth
 @example
 <div><code>
 let monoSynth;

 function setup() {
   let cnv = createCanvas(100, 100);
   cnv.mousePressed(triggerAttack);
   background(220);
   text('tap here for attack, let go to release', 5, 20, width - 20);
   monoSynth = new p5.MonoSynth();
 }

 function triggerAttack() {
   userStartAudio();

   monoSynth.triggerAttack("E3");
 }

 function mouseReleased() {
   monoSynth.triggerRelease();
 }
 </code></div>