Build a chord from a root note and quality (major, minor, dim, aug, maj7, min7, dom7, dim7, half-dim7, sus2, sus4, maj6, min6). Notes are spelled by stacked thirds (C dom7 → C E G Bb). Returns the note names, MIDI numbers and semitone intervals.

Name the interval between two notes (`to` at or above `from`) — its size in semitones, its diatonic number and its quality (perfect/major/minor/augmented/diminished). Correct spelling matters: C→F# is an augmented fourth, C→Gb a diminished fifth.

Parse a note in scientific pitch notation (e.g. "A4", "C#5", "Bb3") into its letter, accidental, pitch class (0..11), octave, MIDI number and frequency in Hz (A4 = 440 Hz).

Build a scale from a root note and type (major, natural-minor, harmonic-minor, melodic-minor, dorian, phrygian, lydian, mixolydian, locrian, major-pentatonic, minor-pentatonic, blues, chromatic). Heptatonic scales and modes are spelled diatonically (F major → F G A Bb C D E). Returns the note names, MIDI numbers and semitone intervals.

Transpose a note by a (possibly negative) number of semitones. Result is spelled chromatically with sharps, or flats when `preferFlats` is true.