Virginia alt-rock band Carbon Leaf has been building a following in and around the Mid-Atlantic area for 15 years now. While they've scored some national radio play with recent albums, they remain more of a regional act, always drawing a better crowd in Richmond or Washington than just about anywhere else in the country. So when the holiday season rolled around, it was no surprise that they filled up D.C.'s 9:30 Club for a special Christmas show last Thursday, which found the band in a very seasonal, and surprisingly mellow, state of mind. Carbon Leaf's headling set was preceded by a member of the band's touring lineup, keyboard and accordian player Tom McCormack, who played his own songs mostly solo on acoustic guitar. He came off a little unsure of himself, constantly thanking the band for the opportunity to play his songs in front of such a big crowd, and the songs themselves tended to be simple, unimpressive variations on the riff from Led Zeppelin's "Ramble On." Carbon Leaf frontman Barry Privett walked onstage in an unusually formal jacket and tie, surrounded by Christmas trees, lights, and wreaths all over the 9:30 Club. And from there on out, the night's mood remained relatively staid, especially compared to the band's more overtly celebratory annual St. Patrick's Day appearances at DC101's Shamrock Festival that play up their Irish-American roots. Though they didn't shy away from better singles like "The Boxer" and "What About Everything?" on Thursday, the two-hour set was clearly designed to primarily please die-hards, or perhaps just themselves, with obscure cuts from early albums like "Attic's Flower Box Window." After Carbon Leaf finished its initial set, the first encore began with just the band's rhythm section returning at first, for a long instrumental medley running through several Christmas songs. And though the holiday selections at first came off a bit tedious, the jazzier elements of the trio's renditions eventually paid off with the most impressive displays of musicianship of the night, particularly Jason Neal's jaw-dropping drum solo. Privett ended the show by inviting the audience to come down to Richmond for their hometown New Year's Eve show, which he promised would be heavy on rarities from Carbon Leaf's back catalog. But it seems more likely that most of the band's Washington area fans would rather wait to see a spirited and crowd-pleasing St. Patrick's Day set than an even more indulgent show than they'd just seen.