In what has to be the worst-kept digital music secret of the year, Facebook plans to announce deep integration with a variety of music services that will let people track their friends’ listening activity on Facebook, join them to listen live in some cases, and find their friends on music services outside of Facebook more easily.

You can watch the Facebook F8 keynote in the video window below (updated: Facebook lists two times for this, 12:30pm and 1pm ET), but we already know a fair amount about what Zuckerberg and company plan to announce, music-wise. Here’s a sampling of what we know so far:

• Facebook and Spotify plan to help people listen to music together at the same time (May 25).
• Facebook Music is old news, with one big exception: real-time group listening (June 20).
• Music needs ‘connective tissue’ between various music services, and Facebook wants to build it (September 1).
• MOG rolls out a free, gameplay-enabled music service, in part to enable Facebook users to play music instantly without whipping out a credit card
• Remastered Rhapsody will probably have the same feature other services do for listening to the same song at the same time (September 15).
• Pandora will let people see what their Facebook friends are listening to, and, most likely, join them (September 21).
• Myxer will definitely allow people to join their friends via Facebook to listen to the same thing at the same time in listening rooms, meaning that Pandora and the rest almost certainly will too, because they’re bigger listening services than Myxer (September 21).
• Facebook will only allow licensed services (as opposed to Turntable.fm) to use “their pipes” to allow people to listen to the same thing at the same time (September 21).
• Facebook’s new real-time activity feed makes the most sense as a place to introduce listening activity (September 21).

You can watch the announcement here or any number of other places: