In Space Blaster, by the player is a blue square object called 'Scroller'. That uses the Bullet movement to move up the layout slowly. The events scroll to that object, but it is invisible so you can't see it.
To loop some music, use the 'set looping' action after the 'play' action in the audio object. Note not all browsers support looping - you might want to try a few (Internet Explorer, Firefox, Chrome).