So yeah we have Quiet's Theme sung by Stepanie Joosten and "First and Last Words" from the extended soundtrack, but neither official OSts nor any Gamerip I've found has had the various renditions of Quiet's Theme either hummed or just instrumental like the one that plays here(Starts at 22:09, Spoilers for the Game btw) :

https://www.youtube.com/watch?feature=player_detailpage&v=KUIp-XyW_R4#t=1330

Does anyone have all the Quiet related tracks?

Thanks.