[laserbeam]

I mean... Spotify tracks a bunch of cool (algorithmically measured) sets of metadata for each song. Basically the ones you have on this site. And there are APIs to retrieve them for any song, and you can use them all as arguments for search. I don't see why you wouldn't be able to find a thing in between two things.

Keep in mind that the actual accuracy of those metrics is debatable. They are cool... But mostly for funzies, or for approximate sorting in 3rd party tools.