Hence the new sound in the band's new album, "IV," which was released Tuesday.

Oh, it has all your basic bluegrass ingredients -- banjo, mandolin, guitar, fiddle, high and lonesome vocal harmonies -- and it has some tunes you'd have to call straight-out bluegrass numbers. But Chatham County Line continues to stretch its wings on this album, using bluegrass instrumentation as a way to explore other musical traditions.

"When we started, we were trying to be a bluegrass band. We really looked up to the staples ... of this music," said lead singer and guitar player Dave Wilson. "Then we realized we don't really need to be that."

"A lot of people say they want to be Sylvia Plath or Edgar Allan Poe, but now we're like, 'Wait, I want to be Dave Wilson -- I want to be me,' " he said. "We want to be a part of history. We just want to be a band. We play great together ... and what comes out comes out. At the end of the day, we don't worry too much if it doesn't sound like traditional bluegrass or rock. What it sounds like is us."

With producer Chris Stamey at the helm, IV is a collection of tunes that don't fall neatly under any particular label.

"They have always stayed true to their traditional instrumentation, but their albums have never been limited by that in any way," said Stamey, former member of the influential dBs and producer of acts including Yo La Tengo and Alex Chilton. "There has always been a progression. They've used bluegrass as a jumping-off point, a vernacular through which to access all that is roots music, be that gospel, country, rock or pop. That is American music, and they are an American band."

Before hitting the road for an extended tour, the band will play two CD-release shows in the Triangle this week: at Cat's Cradle on Friday and at Lincoln Theatre in Raleigh on Saturday.

Wilson described the new album's sound as "less folky, less traditional bluegrass, more melodic and more bass." It includes some piano work by bass player Greg Readling, as well as "little shades" of other instruments that aren't credited on the CD sleeve.

"There's a large maturing with this album," Wilson said. "Getting older, you kind of realize what your world's about, how you are, what's your job. We're at grips with who we are."

John Teer, who plays the mandolin and fiddle and sings the high harmonies, said the focus on "IV" was the songwriting and the songs themselves.

"We wanted to be a bluegrass band when we started, but we'd always had a rock-and-roll background," he said. "Over time, this vibe of rock music kept coming out in [certain] songs in past albums ... slowly but surely. Just this attitude and this energy -- we have a lot of energy on stage and we love playing live."

Teer said his favorite songs on the new album are "Birmingham Jail," about the 1963 church bombing that killed four young girls, and the freewheeling "Let It Rock."

"'Birmingham Jail,' it's got such a climactic feel," he said. "It's got this reckless abandonment to it. It's got a lot of fiddle in it. It's got this very live, raw feel to it. There's a lot of emotion that's poured into that song ... it's got a real energy to it," he said. "And 'Let It Rock' ... you can dance and move to it. It's really fun to have a good group to play [it]."

Chatham County Line recently returned from a tour of Norway, of all places, where they're a big hit after performing and recording with Norwegian star Jonas Fjeld. Now they're ready to kick off a stateside tour in support of the new record, and they're doing it at the Cradle and the Lincoln Theater, two of the Triangle's top venues.

"I just think that we're finally happy to get back on the road and play," Teer said. "And we're really proud of this record. I think it's our best yet."