setADSR(attack, decay, sustain, release) {
    this.env.setADSR(attack, decay, sustain, release);
  }
Set values like a traditional
 <a href="https://en.wikipedia.org/wiki/Synthesizer#/media/File:ADSR_parameter.svg">
 ADSR envelope
 </a>.

 @method  setADSR
 @for p5.MonoSynth
 @param {Number} attackTime    Time (in seconds before envelope
                               reaches Attack Level
 @param {Number} [decayTime]    Time (in seconds) before envelope
                               reaches Decay/Sustain Level
 @param {Number} [susRatio]    Ratio between attackLevel and releaseLevel, on a scale from 0 to 1,
                               where 1.0 = attackLevel, 0.0 = releaseLevel.
                               The susRatio determines the decayLevel and the level at which the
                               sustain portion of the envelope will sustain.
                               For example, if attackLevel is 0.4, releaseLevel is 0,
                               and susAmt is 0.5, the decayLevel would be 0.2. If attackLevel is
                               increased to 1.0 (using <code>setRange</code>),
                               then decayLevel would increase proportionally, to become 0.5.
 @param {Number} [releaseTime]   Time in seconds from now (defaults to 0)