I am working on a similar project, any idea about how they started? Do they have a huge database of music which they manually/automatically fetched from soundcloud/Youtube/other services? If yes, then how do they fetch new songs coming in?
I want to create a database similar to Bop.fm's database of songs with just one service, using which I can use in another app.
P.S. They don't have a public API. :/