Scott and Seth Avett used to wind down after gigs with their rock band Nemo with post-show hootenannies. The alt-country trio has since become the Avetts' full-time group. Joined by stand-up bassist Bob Crawford, the Avett Brothers layer three-part harmonies over bluegrass tunes that often drift into pop and punk territories. The North Carolina band has maintained a busy tour calendar that rivals its prodigious recording schedule — which has yielded six albums, two EPs, and a pair of live records over the past eight years. Emotionalism, from 2007, tightens the screws and polishes the chassis on the Avetts' Americana, offering a strong batch of songs that range from the lonesome country rag "Paranoia in B Major" to the flamenco-flavored flower-power rave-up "Pretty Girl From San Diego." It's restless, ambitious music that never sits still for long.