I haven't used swish in a long time, but what i remember is that when i made a background music player thing with on off function i just used an onclick to start or stop the music action, try making a seperate action (or scene, or what they call it in swish nowadays, just use flash by the way

) for your music and set it on a continuous loop, then you make the onclick to go to the action or execute the action and when clicked again to stop this action