mult(num) {
    var mult = new Mult(num);
    var thisChain = this.mathOps.length;
    var nextChain = this.output;
    return p5.prototype._mathChain(this, mult, thisChain, nextChain, Mult);
  }
Multiply the p5.Envelope's output amplitude
 by a fixed value. Calling this method
 again will override the initial mult() with new values.

 @method  mult
 @for p5.Envelope
 @param {Number} number Constant number to multiply
 @return {p5.Envelope} Envelope Returns this envelope
                                    with scaled output