Dutch entrepreneur and developer Yvo Schaap took a look at the HTML for all the major music services and found that several had references in meta tags to what appears to be a custom Facebook format.
Specifically, Schaap found Spotify, MOG, Rhapsody, Soundcloud, Rdio, Deezer (France), and VEVO all seem to be tagging their songs to be Facebook-compatible.
Among the notable services absent from the list are Pandora and Napster. Pandora has been thought to be among Facebook's most likely partners for adding music streaming to its network.
Schaap explained briefly on his blog what he thinks he's found:
The undocumented mentioned audio type audio/vnd.facebook.bridge seems to refer to a format that bridges audio between the streaming services and the Facebook platform.
It seems all the partners are ready: free streaming, link between the music service and Facebook, all we need is to wait few more days.
Facebook is widely expected to announce the details of a new music service at its F8 conference on Thursday. There have also been reports that some sort of stronger relationship between Facebook and Hulu will be announced at the gathering of developers.
Whatever Facebook announces, it will come just one week after Rdio and MOG both joined Spotify in offering a free account option. Clearly, the floodgates are beginning to open in the streaming world.