Chris Funk, second from right, says Black Prairie is a proving ground for new ideas.

Every toiling indie musician dreams of getting into a breakout band, selling hundreds of thousands of albums and filling venues all over the country. But for members of the Portland, Ore.-based tweed-pop group the Decemberists, whose most recent album, 2011’s “The King Is Dead,” hit No. 1 on the Billboard charts, the band’s growing success seemed to close off more creative avenues than it opened.

“You make your 10 songs and then you go on the road for two years,” says guitarist Chris Funk, “and that’s it.”

Chafing against that grueling touring cycle, he and two other Decemberists founded the side project Black Prairie with vocalist Annalisa Tornfelt and guitarist Jon Neufeld in 2007. “The band started as an experiment and a reaction to our other group,” Funk says. “It was just a chance to do something that felt different.”

At first, Black Prairie performed only in members’ homes, writing and playing instrumental compositions steeped in old-time folk, bluegrass, country and jazz. Audiences back then consisted solely of the band members and their pets. Before the band had even played a public show, it signed with venerable country/bluegrass label Sugar Hill Records and released its debut, “Feast of the Hunter’s Moon,” in 2010.

With the recently released follow-up, “A Tear in the Eye Is a Wound in the Heart,” the band’s mission remains the same: Keep it casual, even when touring.

“We’ll go tour for three or four shows, then come home,” Funk says. “It feels like a long weekend celebrating music instead of having to promote, promote, promote.”

In addition to the new album, Black Prairie also wrote music for “Storm in the Barn,” a play at the Oregon Children’s Theater, and released a limited-edition single featuring the Shins’ James Mercer.

The band has turned into a primary outlet rather than a mere Decemberists side project. “Black Prairie feels very necessary and exciting and permanent,” Funk says.

Inside Track: Vocalist Annalisa Tornfelt wrote “Richard Manuel” — about the suicide of The Band’s pianist/singer — when she was a teen. She “takes you into his misery,” Chris Funk says.

Iota Club & Cafe, 2832 Wilson Blvd., Arlington; Fri., 9 p.m., $12; 703-522-8340. (Clarendon)