This trendy fellow is a Boards of Canada fan.
Valve is bringing an in-game music player to the Steam overlay, which will allow you to listen to your own tunes while playing your games. The main announcement says the feature is going into beta soon for Big Picture mode and SteamOS, and there are plans to bring it to the standard desktop version soon as well.
Those interested in joining the beta should find the group “Steam Music” and join. That’s it. Entrants will probably be picked at random, just as they are for the In-Home Streaming.
Right now, only the mp3 file format will be supported, but Valve states there will be support for others in future. “With this beta, we’re getting started with what we believe to be the most fundamental set of features to offer a great music listening experience within Steam,” the company adds.
