North Carolina trio Avett Brothers once sounded like Appalachian Beatles: chirpy harmonies over effervescent acoustic guitar, banjo and upright bass. They've gotten moodier in recent years, and for their major-label debut, producer Rick Rubin has turned the group into a lush chamber-folk outfit. I and Love and You is packed with complex, piano-based beauties. "They say, 'Don't take your business to the big time,'" sing the Avetts to any doubters, adding, "I bought us tickets there."