Few musicians try to scale peaks as high as those attempted by Will Sheff. The front man of Austin’s Okkerville River doesn’t think small; his lyrics are prosaic but frequently impenetrable, his arrangements grandiose. Even his singing is nervy; he struggles, often out of his range, to get his voice over the top of his band’s sonic density. Particularly early on, this overreaching resulted in some notable plummets. But since 2005 Sheff and his band have released a trio of tight, conceptual albums ( Black Sheep Boy, The Stage Names, The Stand Ins ), each better than the last, and their following has blossomed. Now, after taking a year off to work on a collaboration with psychedelic hero Roky Erickson, Sheff has thrown Okkervil’s latter-day working model out the window. I Am Very Strong (Jagjaguwar) is a glorious mess of an album, at once fascinating and disjointed. Producing his band for the first time, Sheff called in huge lineups (two drummers, two pianists, seven guitarists) to play live in the studio and tossed everything he had into the arrangements—choirs, horns, strings, even, according to the liner notes, a file cabinet. On ballads and rockers, the music builds until the listener is all but exhausted. Sheff wrote and rewrote the typically bleak fare, which ranges from ghost stories to weird science-fiction epics, then edited and reassembled the material throughout the recording process. The results are all over the place but clearly the work of a singular vision.