For years now, Van Morrison has been resolutely chipping away at his own myth: The sublime Celtic poet, the transcendental visionary of Moondance and Astral Weeks — nothing would please him more than to see those images crumble and fall away. Morrison’s third record in less than two years is earthy, barreling blues, R&B and country-tinged roots rock, all delivered with enough gusto to strip the enamel right off your teeth. His partner here is pianist Linda Gail Lewis, sister of the great Jerry Lee Lewis, who ably shares vocals and propels the duo through a motley but rousing grab bag of covers, including John Lee Hooker’s “Boogie Chillen’,” Hank Williams’ “Jambalaya,” Otis Blackwell’s “Let’s Talk About Us” and — only Morrison could say why — Stephen Foster’s “Old Black Joe.” The thirteen songs are all live takes recorded in a couple of extended studio workouts, with all the rough edges proudly exposed. Occasionally, he gets what he’s after. Morrison’s voice — cracked, insistent and soul-searching — is still a wonder in its ragged glory. Between the lines, you can sense him probing for that old spark. This is muscular, pub-crawler stuff, machine-tooled for a workingman’s Saturday night. For Morrison, though, it is invigorating, and clearly a refuge.