It’s definitely a Bulgarian female choir for the polyphonic vocals, so either the Time of The Gypsies soundtrack, Trio Bulgarka, Le Mystère des Voix Bulgares, or similar. It’s been a while since I’ve seen it, but I’m about 75% certain it’s from Time of the Gypsies.
I’m not musical enough to tell if it’s overlain by, or accompanied by, the orchestral stuff, but it’s definitely Bulgarian/Balkan polyphony.
Huh. I just did a quick search—it looks like the new Galactica soundtrack does feature Bulgarian vocals. I would never have recognized them, and it does narrow things down quite a bit. I tip my hat!