Before you ask.
Will it slow down my Mac or drain the battery?
No. It waits for something to happen instead of constantly checking. With music paused it uses around 1.5% of one processor core and 36 MB of memory.
Does my Mac need a notch?
No. On Macs and external displays without one, Brimtune shows a small floating island at the top centre of the screen, and only when something's playing.
Which music apps work?
The Apple Music and Spotify apps, and YouTube Music or Spotify in Safari or Chrome. For covers, progress, Up Next and your playlists from the browser, turn on Allow JavaScript from Apple Events in that browser: in Safari it's under Settings, Advanced, "Show features for web developers", then the Developer tab; in Chrome it's View, Developer. The setup guide shows you where and checks it's on.
Why does macOS warn me the first time I open it?
Apple only skips that warning for developers in its paid programme. Brimtune is signed by its maker, so macOS asks you to confirm once in Privacy & Security. After that it opens like any other app, and updates keep your permissions.
What does it do with my data?
Nothing leaves your Mac except the song details needed to find lyrics and covers. There's no account and no tracking. The privacy policy lists exactly what goes where.
Is Brimtune open source?
Yes. The code is on GitHub under the GPL-3.0 licence: read it, build it yourself, report a bug or send a fix.
How do I remove it?
Choose Quit Brimtune from its menu bar icon, then drag Brimtune from Applications to the Bin. To remove its history too, delete the folder Library/Application Support/Brimtune in your home folder.