So, I finally got my hands on the Series 9 soundtrack, and I have to say I'm slightly disappointed.
Despite having four (count 'em, FOUR) discs, it's actually shorter than the Series 8 soundtrack which only needed three, and the fact that Heaven Sent and The Husbands of River Song each have a disc to themselves means the episodes are out of order (which annoys me more than it should, especially since H-E-Double-Hockey-Sticks Bent only had four short tracks that could've easily been tacked onto the end of Heaven Sent's disc).