i dont know if u even want the music change when u get close to an enemy but heres a demo just look at the event & variables on this demo
http://www.megaupload.com/?d=IHT03FQIcredit to aqua & shdwlink1993 the helped me with the distance mini script with was used in this demo
with i will add to my abs ad on when i fix a few things
i added blabs sice thats what u were wanting it for