You can download every last one of Kirill's tracks from the Divinity series at his website
here. They recycled a lot of his old stuff in this game.
Nope, that's nearly not every song that ever was in a Divinity game. Divinity 2, Dragon Commander, Original Sin did not have a complete soundtrack.
Original Sin has ~140 music tracks, sure there are recycled and remixed tracks from previous games, but there is also A LOT of new tracks that are not on the soundtrack (and also not on the website)
If you are looking for a specific track from original sin (or the complete OST for hat matter) look into converting wem to ogg, as mentioned above.
