Type Alias NoteData

A spelled note: a diatonic letter, a chromatic alteration, and an optional octave.

• letter is 0..6 for C..B.
• alter is the number of semitones of alteration: -2 double-flat, -1 flat, 0 natural, +1 sharp, +2 double-sharp.
• octave follows scientific pitch notation (middle C = C4 = MIDI 60). When absent, the note denotes a bare pitch class.