Maps each clef to the corresponding note at position 0 (which is on the middle bar of the staff).
Remarks
The value in the map is not a MIDI note number (which is based on a 12-notes octave),
but a note number based on a 7-notes octave. Only note 0 corresponds to MIDI note 0.
Maps each clef to the corresponding note at position 0 (which is on the middle bar of the staff).