Crankshaft FM

Crankshaft is a free iOS and CarPlay app that plays your existing Apple Music library using a different set of weights than Shuffle does.

It does not use hearts, thumbs or stars. It reads behavior: the songs you let finish, the ones you skip and how fast, and what you do with the volume. Reaching for the volume when a song comes on is a signal almost nothing else captures. Those signals feed a coverage rule, so your whole library stays in rotation instead of collapsing to the same forty songs.

Everything runs on the device. There is no account and no sign-up, and Apple's privacy label for the app reads Data Not Collected.

Crankshaft requires an Apple Music subscription. It plays your library and is not a replacement streaming service. It also needs a few sessions of real listening before it is useful, because it learns from behavior and starts with none.