I love that it's working by sound. So often eg Spotify will insist I check out other bands in the same "scene" or from the same era as other artists I like, and in genres as broad as "70s rock" it can be really tiring.
One of the first tracks I tried was Natural Woman by Carole King. I love that it recommended other slow but rhythmic piano vamps with tender vocals by artists singing in other languages, some modern, some old, as well as some sung by men. It even recommended me more Carole King which is I guess shows it's picking up on something constant in her music.
What impressed me was that it recommended quite a lot of numbers in the same key! It was funny clicking through them and the tonal centre being unchanged. It was like they really were different but the same.
It definitely doesn't understand everything about tonality though! I tried some atonal music next, Naama for solo harpsichord by Iannis Xenakis, expecting to get more atonality back. Nope, first result was very firmly tonal: "Suite in E flat major" by Bach for solo harpsichord. It definitely got some essential aspects of the pieces down but completely missed the central concepts underpinning their musicality.
Very promising like I say, can't wait to try more things out!