A main aspect of Facebook Music will be Scrobbling. The term, made popular by Last.fm, means that when you listen to a song, its title, album and group gets sent to your profile without you have to do anything. It is a post-music-to-profile feature. Facebook’s core feature is the wall feed, and music will now make it even more robust.
A desktop software team at Facebook was working on a scrobbler client that could also work with iTunes (and Winamp) to import listens. Those tracks could then be matched and played via Spotify, MOG, Rdio, etc, on Facebook Music itself.
Facebook Music will also apparently offer content resolution between all the different music partners involved. This means that if you are listening to Spotify and a track goes up on your profile, a MOG user can click on the track and still hear the exact same song in full. Essentially, you’ll only need to sign up for one of the major music services Facebook is launching with to be able to access most content.
This content resolution will likely be the most important aspect of Facebook Music. It turns Facebook into the great social music unifier.
There will be a standard online player that plays music without interruption from page to page as you browse Facebook. There will be persistent controls and another section with a larger Music Dashboard area. The player would be at the bottom of Facebook, but they are still making tests about its final position.