Track 01 on the Aldnoah.Zero Original Soundtrack is a vocal piece titled "No differences" (lyrics). It's positively eargasmic. Thing is, I don't remember it being played at any point during the show (and, given that the lyrics are English, I feel like I would have remembered it if I had heard it). Was it used? If so, when?
(Yeah, I could just rewatch it and listen for the track, but that would take a few hours I don't want to spend right now.)