These crusty Southern punks outed themselves as prog rockers in 2008 with a brilliant cover of Pink Floyd’s “Set the Controls for the Heart of the Sun,” turning that late-’60s space shuttle into a battle cruiser. Then, last year’s breakthrough Static Tensions found an audience ready for their sludgy guitars, double-drum thunder, and guitarist Laura Pleasants’ earthy scream. The 78-minute Spiral Shadow supersizes everything, from song lengths to layers of deep-focus space-rock effects, but the sprawling songs are still built around riffs as sweaty as a south Georgia summer.
