“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 shined up the rootsy, harmony-laden sound 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.”