That was my first thought, too. There's probably something wrong with me haha
My university choir sang this back to back with Billings's "I am the Rose of Sharon." it was beautiful.
As a musical director of a collegiate a cappella group, we bought this arrangement and began learning it. Th learning process became very frustrating (we learn on solfege primarily, not by rote), and I went to our choir director to ask for tips. He said "You're really reading this in the a cappella group? This is the kind of thing I'd give to our chamber singers" (a legitimate professional ensemble). It's a damn fine (and damn hard) arrangement.
Just look up a chart of the tune and learn the changes :)
What was that blues tune near the beginning?
4:36 when that swung bass drum pattern slowly morphs into a 3vs2 polyrhythm. uuuuuunh. Love
Check the description :)