There comes a moment in every Slim Cessna’s Auto Club show when you realize you’re seeing something you’ll never see anywhere else. It’s Slim Cessna in a white cowboy hat and beard, the lights haloing his ungainly frame, horn-rimmed glasses flashing through the smoke. He’s trading lyrics and insults with Munly Munly, gaunt and strange, dressed in a shade of black particular to preachers and burnt down barns. Their voices rise and converge in the kind of exquisite harmony usually found in Sacred Harp congregations, and then the band cuts loose, the best live band in the world, and the two men are doing battle, playing out some cathartic war between good and evil on stage. Or trading dance steps. You can’t tell.