addPhrase(name, callback, array) {
    var p;
    if (arguments.length === 3) {
      p = new Phrase(name, callback, array);
    } else if (arguments[0] instanceof Phrase) {
      p = arguments[0];
    } else {
      throw 'invalid input. addPhrase accepts name, callback, array or a p5.Phrase';
    }
    this.phrases.push(p);
    // reset the length if phrase is longer than part's existing length
    if (p.sequence.length > this.length) {
      this.length = p.sequence.length;
    }
  }
Add a p5.Phrase to this Part.

 @method  addPhrase
 @for p5.Part
 @param {p5.Phrase}   phrase   reference to a p5.Phrase