“They say ‘Don’t take your business to the big time’; I bought us tickets there,” sing The Avett Brothers on “Slight Figure of Speech,” summing up their major label debut. With producer Rick Rubin, they streamlined and polished the rootsy, harmony-laden sound they’d developed over previous albums. There’s gravity to these chamber-folk ballads, from the majestic piano-based arrangements to the hard-won lyrical wisdom. And they prove they still know how to get a bluegrass hoedown started on the rollicking “Laundry Room.”