The latest Bonnie “Prince” Billy album elevates The Cairo Gang’s main man, Emmett Kelly, from bit player to key collaborator, making prominent use of the avant-folkie’s voice and guitar as they wind easily around Will Oldham’s. The Wonder Show Of The World relies equally on Oldham’s in-the-moment spontaneity and the kind of ghostly after-the-fact orchestrations that Kelly brings to his own work. The album-opener, “Troublesome Houses,” sets the tone, coming out rhymeless and rhythmless: Its hook is little more than a two-note guitar signature, joined by little wisps of sound, as though friends wandered by, dug what Oldham and Kelly were doing, and were inspired to pick up their own instruments.