code: function Note( str ) {
    var couple = str.split( space );
    // frequency, in Hz
    this.frequency = Note.getFrequency( couple[ 0 ] ) || 0;
    // duration, as a ratio of 1 beat (quarter note = 1, half note = 0.5, etc.)
    this.duration = Note.getDuration( couple[ 1 ] ) || 0;
  }
docs: /*
  Note class
  
  new Note ('A4 q') === 440Hz, quarter note
  new Note ('- e') === 0Hz (basically a rest), eigth note
  new Note ('A4 es') === 440Hz, dotted eighth note (eighth + sixteenth)
  new Note ('A4 0.0125') === 440Hz, 32nd note (or any arbitrary
  divisor/multiple of 1 beat)
  
   create a new Note instance from a string