Backstage after a sold-out show in New York, Justin Vernon — who records haunting, strummy folk rock as Bon Iver — is hiding out in his dressing room. Outside, friends are knocking on the door, a joint is making the rounds, and his tour-rider-mandated 12-pack of Heineken has long since been emptied. A rowdy bandmate yells from outside, "Are you done having sex yet?" Vernon runs a hand through his shaggy hair and exhales. "You have no idea how much I don't want to deal with that...