Angel Olsen’s voice is disarming. On “Acrobat,” the opening track from her 2012 album Half Way Home, Olsen plays a simple guitar melody before her powerful, tender vocals show up to take it from there. Her voice isn’t just a lyrics dispenser, but an instrument, blowing ethereal whispers and quaking with an otherworldly vibrato. Many of her songs veer toward the atmospheric and strange, but Olsen also borrows from country, doo-wop, and even flamenco traditions. It shouldn’t matter whether Olsen performs at DC9 solo or with a band; her voice is its own attraction.