ACC or ON when I'm listening to music in the 08 G35
 

so I was wondering when the 08 G35 sedan is off should I leave the car in ACC or ON to listen to music?

in my caddy I put it to ACC and it goes for 15 minutes but automatically turns to off without telling me and keeps playing music and then it kills the battery

leaving the car in "ON" primes the ignition system and energizes a host of other electrical systems, so if you were forced to choose one setting, i'd just leave the car in ACC to listen to music.