Wow this is super cool!

They primarily used the genius.com API, which I didn't know existed. Anyone built any other cool projects with it?

Is there a "discovery" player that plays your own Spotify library, but shows you all related tracks by sample, interpolation, cover, etc from the Genius API that you can explore? Kind of like a wikipedia rabbithole, but for music?

We used it to allow pepole to include song lyrics in their letters sent to loved ones. Unfortunately it was a constant source of breakage in the app and we eventually removed it when they pushed a very breaking change and there wasn't any availability to rewrite that part of the app.