Go to the "music" directory in your install folder and delete all the subdirectories starting with B (bc1, bc2, bd1, etc) - leave the bptheme one. This will disable the combat music, but leave other music in the game. Alternatively you can move them into another directory instead if you want to be able to enable the combat music again later on.
If you're unsure whether or not a folder contains combat music, look at the files in it. Combat music is made up of several small sound clips including a few with "end" in the filename - this is so that the music can be naturally ended without an abrupt cutoff on short notice once combat ends. Other music tends to consist of just one larger file.
The battle music can be repetitive, but I still love the bg1&2 soundtracks. I have this strange addiction to the music that the inns play. It can't be healthy.
Comments
If you're unsure whether or not a folder contains combat music, look at the files in it. Combat music is made up of several small sound clips including a few with "end" in the filename - this is so that the music can be naturally ended without an abrupt cutoff on short notice once combat ends. Other music tends to consist of just one larger file.