Click Play to hear the music. Click any note to fast-forward and play from there. Space plays/stops; in Oneshot mode ← / → play the previous/next note.
Shift+click a note to mark the loop start (A), then another note for the end (B) — Alt+click moves B. Keys: [ / ] mark A/B at the current note, L turns the loop on/off, \ clears it.
Colors show each note's distance from the tonic — the first note of the score by default. Ctrl+click (⌘+click) a note to start a new tonic there; ↑ / ↓ or the +/− buttons move the selected tonic by a semitone, ✕ removes it. Any number of modulations can be marked; each one colours the music from its note onwards.