There is a delay, but it should stop eventually. Are you sure it NEVER stops?
It may be possible to turn it off via a mod, or to simply delete the relevant files, but I don't know which files that is. Was sure I had seen a mod that does this, and there must be one somewhere, but the one I thought about was for Planescape Torment I think.
A workaround can be to turn off music in the options, but that will obviously remove all music.
EDIT
Nice, came over this thread:
http://forum.baldursgate.com/discussion/3750/sound-options-separate-sliders-for-battle-music-and-ambient-music If that bloke is correct, you can remove the battle music entirely by removing the folders named "B..." in the music folder. If it doesn't turn off at all, you can always try that. I find the battle a bit annoying myself actually, so this is good to know if it gets too much on my titties.