Facebook product designer Alexandre Roche explained the new feature in a company blog post:
This feature lets you listen along with any of your friends who are currently listening to music. You can also listen together in a group while one of your friends plays DJ.
It works like this: Friends who are listening to music via any one of the available music services on Facebook will have a music note next to their names on the Facebook chat sidebar. The “listen with” button will appear when you hover over a name that has a music note next to it. Once you click that button, you will hear the exact same thing that your friend is hearing at that time.
The “listen with” feature brings to mind turntable.fm, an online music service that lets people create music listening rooms and share DJ duties with their friends. Turntable.fm became a big hit this past summer, and closed on $7 million in venture capital in Sept. 2011. But there are a few major differences between “listen with” and turntable.fm. For one thing, turntable.fm allows anyone to listen to music together, while the “listen with” feature only connects people who are already Facebook friends. And while turntable.fm allows people to create colorful avatars that can be made to dance along to the music, Facebook’s new feature is visually much more bare bones.
“Listen with” will roll out to all users over the next few weeks, Facebook says.