When the art-metal duo of Greg Anderson and Stephen O’Malley, known collectively as Sunn O))), last visited the Classic City, they performed at the Seney-Stovall Chapel. As audiences entered the chapel, they found that the center of the room had been taped off, as if in waiting for some heavy metal VIPs. In fact, it was for reasons pertaining to safety rather than elitism: The band’s soundcheck made the chandelier immediately above the seats in question shudder ominously. Armed with their signature battery of amplifiers, Sunn O))) proceeded to shake light bulbs from their fixtures and set off the chapel’s security alarms solely using weaponized sound. Theirs is a music rendered viscerally physical, eschewing a rhythm section in favor of a pure harmonic thrall.