Steam is on a warpath for integrating as many functions as possible into the platform. Valve recently announced the beta test of Steam Music; which will be coming to Steam’s Big Picture and SteamOS very soon.
Like any other music player, it will play your music files stored on the computer. Although the integration makes it easier to listen to music while playing games. The idea is that it works through the Steam overlay on games, and allow the creation of playlists in the middle of games. Without having to switch over to a different program.
The upcoming beta test will only be able to play MP3 files, although this is set to change over time. Naturally, the Steam community board is already swarming with requests and suggestions on what features should be implemented next.
Those interested in joining the test can do so by signing up in the Steam Music group in the community. Users will be chosen at random from this group to participate in the test. If this is anything like the Family Sharing beta, it might just means everyone in the group gets to try the beta program.