They do a bit of role-switching in Bleak.
You can hear SW doing the high notes but I think the second lines, "moved me from relief", "and filters through me" are done by both.
I don't know, but to me it sounds like the "you're close to the final word" part is done by Mike. You can hear how SW sounds pretty effortless hitting high notes, but that part sounds like Mike because seems to struggle more with the high notes (as can be heard in the Roundhouse Tapes) to me, making me guess that's Mike harmonizing with himself.
Also, "night falls again, tainting what's left of me" sounds clearly like Mike to me.
I think SW also plays the solo in this song?