Allow for user groups where people can actively share songs with one group or another. From there the ranking begins. Upvotes/downvotes work, but the Facebook style of choosing a "type of like" is much more useful in the long run.
Trying to rank songs without any context is almost impossible. You'll just end up with one particular style that is popular for the entire site.
I am definitely open to further experimentation but so far users have enjoyed the ranking process and it is easier to say I like this song more than this song than it is to say this song is good vs bad.
Also the upvote downvote system is ripe for abuse comparatively. Because LaunchSong doesn't let you link to a song to rank it gives artists without an existing audience a level playing field (because people cannot say go upvote my songs). Furthermore the elo rating system lets newer songs climb more quickly