code: function(bpm, beatUnit) {
      var secs = (60 / bpm) / (this.duration.value / 4) / (beatUnit / 4);
      return secs * 2 - secs / Math.pow(2, this.duration.dots);
    }
docs: Returns the duration of the note (including dots)
  in seconds. The first argument is the tempo in beats
  per minute, the second is the beat unit (i.e. the
  lower numeral in a time signature).