Hi,
welcome to this forum.
I am not very sure about your question, I think that a little while ago somebody asked the same thing and apparently you need a special plug-in, but only to get some kind of wav recording which is rather large.
It seems that it's very hard to extract music information out of a game, to make some sort of midi file for example,because of the way the memory is organized.
I have another system which works with anything though.
My soundcard (creative soundblaster live!) came with a little recorder program that let me record anything that's played through my sound card, being it a videogame score or a movie or me when I do karaoke !!
I get then a large .wav file, but my trick it's actually to import this file to iTunes(free) and convert it to a much smaller MP3 file.
Sorry if you were looking for something else, this is just my way to do it and it works for me.
Take care