Trying to find a music streaming app that has the best algorithm for finding like 'sounding' songs

I'm not sure how apps, like Pandora, work for finding songs to play in a mix when creating a radio station based on a single song. They all seem to work by cycling a catalog of songs from that artists along with 'like' artists in a genre.

What if I want a radio station that plays similar sounding songs, regardless of genre, age, or etc? Is there an app for that?

Suggestions welcome.

Cheers!