In its bid to take over living rooms and, indeed, whole homes, Steam's getting a new music feature buckled onto it. The beta will hit Big Picture and SteamOS soon, desktop features coming later, letting you use Steam to play music while you game, but we can already gawp at screens and see what the big deal is.
Although it's accessed via Big Picture, users with mouse and keyboard can still get to the active player through the Big Picture menu. With a Steam Controller, you just need to hit the Guide button. One in-game, you can control the player via the Steam Overlay.
The beta is just about getting the fundemental features on there, but SteamDB spotted references to Spotify when they investigated last year.
Having not used anything but Spotify for the last year, I wouldn't want to give up my playlists just to control music from the overlay, so Spotify integration would, at least for me, be a necessity if I was to ever use it.