Joy Williams and John Paul White bring a modern edge to the traditional Americana genre with their breakout band the Civil Wars.

Joy Williams and John Paul White had no intentions of making music together, but as with most things related to the Tennessee-based Americana group the Civil Wars, the partnership came about without trying. The two met at a songwriting workshop in Nashville in 2008 and immediately hit it off.

“Our initial reaction wasn’t, ‘Hey, let’s start a band,’” Williams says. “It was more like, ‘What is this? I’ve never felt this.’ It was something that we couldn’t walk away from. So we wrote some more songs and did a few open-mic nights.”

Now, the Civil Wars have emerged as one of the most surprising grassroots successes in recent years, with a best-selling debut album, February’s “Barton Hollow,” and a track that made the rounds on “Grey’s Anatomy” (the single “Poison & Wine”). They’re at the forefront of a new group of artists looking to old-time country and folk music for inspiration. Yet their influences are diverse, and their music largely unclassifiable.

“I don’t know where we fit,” White says. “We have as hard a time finding a label for us as anybody else does. The Americana tag is such a broad genre that we’re usually placed in, and we don’t shy away from it.”

Whatever you call it, the Civil Wars’ music is austere and largely acoustic, centered on White’s guitar, Williams’ piano and the duo’s lush, startling harmonies. Within that strict framework, they strive to be as wide-ranging as possible.

“If I’m standing up there strumming a guitar, just sawing back and forth all night, it’s going to get monotonous,” White says. “So, we have to be as inventive as we can without being showy. And it all has to make sense as part of the song, because everything that we do hinges around the song.”

That understated approach allows the songs’ emotions to resonate. “It’s not just emotion for emotion’s sake, but people feel like they can integrate their stories into our music,” Williams says. “There’s no way we could phone it in.”

Lincoln Theatre, 1215 U St. NW; Sun., 8 p.m., $30; 202-328-6000. (U St.-Cardozo)