If you hold down the PS button a side-menu comes up. I *think* that side-menu has media controls for the built-in music player, but I haven't used it in a long time so can't 100% confirm. I *do* remember that the controls for music volume playback shows up there.
If I'm right, it should save you having to back up to the home screen to load the music player app to change songs, and keeps WOOC visible in the background (to an extent) so you'll be able to see if the track loads whilst you're still looking for a song.
Other things, such as friends list, options to start broadcasting, restart/rest mode/turn off, etc, are in that little side-menu too. It's pretty handy.