"We haven't played in this town for two years," Scott Avett explained to the eager crowd at the Paradise Rock Club, and in two years, nearly everything has changed for his band. The Avett Brothers were a regional act first, made up of two siblings and one friend, all raised in North Carolina; they last swept into Boston in January 2006, as relative unknowns.
They returned Friday night with a peculiar sort of ballast, one driven in equal parts by a hard-won reputation for raucous stage theatrics, and by academy acclaim (the band recently picked up a pair of Americana Music Association Awards, for best new/emerging act of the year and for best group of the year).
The Avett Brothers, in other words, have grown into themselves, and their fans have grown up with them. They recently released a new album called "Emotionalism," which blends folk harmonies with the insistent trot of honky-tonk and bluegrass; it debuted at the top of Billboard's "Heatseekers" chart.
At the Paradise, in front of a packed house, the Avett Brothers demonstrated exactly how far this stuff can go: through rollicking punkabilly ("Nothing Short of Thankful") and into country sprawl ("A Lot of Movin' ") and balladry ("Pretty Girl From Chile"). It's a dynamism that might seem messy - or worse, distracting - in the hands of lesser artists. Here, it's merely passionate, and at the right pitch, enthralling.
Aligned at the front of the stage, Scott and Seth Avett and bassist Bob Crawford, along with a rotating cast of support musicians, shook and swayed and stretched and shouted and panted, pausing only twice to thank the crowd. The racket was tremendous, filled in with minor-key rags and rangy weepers like "November Blue."
Near the middle of the set, the band walked quietly offstage, leaving Seth Avett to perform a solo version of "My Last Song to Jenny." Avett belted the plaintive opening lines with his face tilted up into the lights: "Oh tell me please/ that I don't have to read between the lines."
It was a neat bit of theater, designed to show that even in the midst of all that orgiastic noise, there was plenty to read between the lines: a wry sophistication, and the Avett Brothers' devotion to songcraft as its own reward.
Opener Christopher Denny has a new CD called "Age Old Hunger," and he sang most of it alone, with only a guitar and harmonica as accompaniment. 
