Give your melody a second voice. Contrapunctus writes counterpoint. Draw a melody on a simple grid — or import a MIDI or MusicXML file — and it composes a genuinely independent second line against it: real first-species counterpoint, obeying the voice-leading rules right down to the cadence. HOW IT WORKS • Draw a melody on the timeline (leave a gap for a rest), import MIDI/MusicXML, or type it in. • Contrapunctus generates a legal counter-line above or below, updating live. • Cycle the distinct valid options — ranked best first — and pick the one your ear likes. • Shape it with two dials: how strictly it favors sweet 3rds and 6ths, and how independently the voice moves. WHAT'S INSIDE • A real rule engine — no parallel fifths or octaves, proper cadences, and a musica-ficta toggle that raises the leading tone in modal keys. • Works in every mode: major, dorian, aeolian and the rest. • Live standard-notation preview of both voices. • MIDI and MusicXML import and export — for MuseScore, Sibelius, Dorico, Finale, or your DAW. • Fully offline. No account, no sign-in, no ads, no in-app purchases. • Private by design — Contrapunctus collects nothing. Your music never leaves your phone unless you export it. Contrapunctus is by Songdeed.