The PLAYBACK is the icon which presents the titles and effects on the stage. You can see the title of the certain song below the PLAYBACK button. If you want to finish listening to the music you should simply pull the selected PLAYBACK button off the stage.
You can pull further PLAYBACK buttons onto a PLAYBACK button to get a list of titles. Keeping the PLAYBACK button pressed for a while, you can open the PLAYLIST EDITOR.