“For these gospel titans’ latest album, Justin Vernon of Bon Iver brought the group to his Wisconsin studio and added sparse production to its lush traditional harmonies. The marriage is not perfect. The various cameos (Sam Amidon, Merrill Garbus of Tune-Yards among them) can make the Blind Boys seem like guests on their own LP. Still, the Boys’ performances are first-rate, and Vernon’s duet with B”