How I wish they would open up that API. It would be so cool to search for music based on attributes, as in "give me a song in minor, with an electric guitar lead, with a virtuosic guitar solo, with female vocals, and with electronic instruments". You can kind of do that now by Googling the Spotify keywords, but it's not perfect. And what if you could create a custom radio based on attributes? Even better!

I fear that if Pandora ever goes away, this immense collection of musical knowledge will go with it.