I actually think they did well on the system it is now, cause to 80% it is what you want. The music only plays, when there is no other music: shops, theme music and just comes in when you pause or in an empty area. Of course it could be finetuned, but i would rather have the smart option than the hardcoded.
And Credit where Credit is due: the soundplay of the game, either background soundtrack or Ambience soundtrack is really good and immersive.