Devs released a free soundtrack DLC on Steam! Thumbs up from me. I don't know if devs remember about GOG, but I do hope it will show up here soon.
I realize that this isn't quite the same thing, but until a soundtrack is released as an extra, all of the music in the game can be found in .ogg format in the Advent Rising\Music folder.
Apologies for the late post, but I thought this information might be useful for anyone who wanted the music but didn't want to have to download from Steam.