_convertNotation(value) {
    var type = value.slice(-1);
    value = Number(value.slice(0, -1));
    switch (type) {
      case 'm':
        return this._measure(value);
      case 'n':
        return this._note(value);
      default:
        console.warn(
          'Specified interval is not formatted correctly. See Tone.js ' +
            'timing reference for more info: https://github.com/Tonejs/Tone.js/wiki/Time'
        );
    }
  }
Convert notation from musical time format to seconds
Uses <a href = "https://github.com/Tonejs/Tone.js/wiki/Time">Tone.Time</a> convention
@private
@for p5.SoundLoop
@method _convertNotation
@param  {String} value value to be converted
@return {Number}       converted value in seconds