Boulder, Colo.-based bluegrass band Ragged Union certainly sound like traditionalists, what with their winsome stacked vocal harmonies and their canonical deployment of the guitar-mandolin-fiddle-banjo-bass format, and the way the band’s stringsmen deftly navigate dizzying ensemble passages…

But listen close, and you’ll notice cracks in the facade of their orthodoxy, the occasional stylistic and songwriting nods to rock ‘n’ roll, and lyrics that often stray far from the hardscrabble hillbilly tropes — on songs like “Rented Room” and “Half Lit Parking Lot” and “Moonshine Boogie,” all from their forthcoming release “Time Captain.”

“I like the sound of traditional bluegrass, the melodic and rhythmic patterns and the harmony singing,” says Union, who founded the band along with wife and fellow vocalist Christina Union. “But I also have a rock ‘n’ roll background, and I’m steeped in the songwriting tradition of artists like Billy Joe Shavers and Townes Van Zandt.

“All of that led to my songwriting being less traditional, with more modern lyrics and sometimes modern arrangements, paired with old-timey melodic ideas.”

North Carolina native Union grew up like so many musical children of the 1980s, playing electric guitar in standard-issue Rawk outfits, even passing through what he describes as a “minor heavy metal phase.” It wasn’t until college — when someone played him an old Doc Watson record, no less — that the mid-20-something Union ditched his pedals and amplifiers and set out in a new direction.

“Bluegrass became a listening and playing obsession for me,” Union says. “It was difficult, at first, going from playing electric guitar to traditional flat-picked acoustic guitar. It took me a lot of years to actually sound like a guy who had been playing acoustic for all his life. But now if I pick up an electric guitar, it freaks me out a little. It’s so easy for me to play, it’s almost disconcerting.”

After playing in a variety of other bluegrass-oriented projects, Geoff and Christina founded Ragged Union in 2011. They eventually settled in Boulder, where built the band around a roster of veritable all-star musicians, including Tennessee native Jordan Ramsey, a national mandolin championship winner, and East Tennessee State University alumni David Richey on bass.

Union says the band’s mix of tradition and iconoclasm makes for a comfortable if occasionally odd fit in Colorado, the state a renowned haven for hippie kids and jam-band aficionados. “The college kids love jam bands, and that crosses over into an appreciation for what we do,” he says. “We do some of those types of festivals, and we’ll pick songs that those folks might appreciate more. The dancers and the partiers love it. But I think, maybe, that the traditional crowds love it just a little bit more.”

Ragged Union will play Preservation Pub Thursday, Oct. 26 at 10 p.m.