Sing along to your own music, with a visible guide to the notes. OnKey listens while Spotify, Apple Music or YouTube plays a song. After that first play ends, it processes the melody; on later plays, your pitch appears over the singer's notes.

Daniel Murrell built this free, open-source Mac app with Claude Code. Local models separate the vocal and extract its pitch and notes. The app allows singing an octave lower and gives feedback on individual lines, rather than requiring a developer-supplied song catalog.

It needs an Apple Silicon Mac and macOS 14.2 or later. Melody processing happens locally; song identification, lyrics and cover lookups can use online services. It is a practice aid, with room for transcription errors.

Watch the creator's demo and see how it works:
singonkey.app/

Image: OnKey's original demo poster, Daniel Murrell.