"They're making the banjo respectable, which is not an easy feat, and I'm so glad it's finally happening," Harris joked.
Harris, an iconic singer and member of the Country Music Hall of Fame, and Mumford & Sons, platinum-selling lads from London who have sparked a folk-rock resurgence, are joining together to explore their shared love of high harmony, sad songs and, yes, the oft-belittled banjo on an episode of "CMT Crossroads" at 8 p.m. Thursday, Sept. 27.
The Nashville-based Harris had only briefly met lead singer Marcus Mumford before agreeing to do the show based on the waves they created in the music world. They coordinated song choices by phone and got together to rehearse for a little more than a day before recording the show earlier this month.
It was a crash course in catalog consumption and the chance to get to know each other.
"They're great harmony (singers) and they've got this great driving groove with a minimalist instrumentation," Harris said. "But they just sound good and the songs have beautiful melodies and I love harmonizing on them."
She said it proves her theory that music is going to keep reinventing itself in good ways.
"You don't have to repeat the past. We learn from the past, but we have to come forward with something different and there are just so many different combinations to make good music that touches people," she said.
Harris, 65, was among the gateway artists who helped Mumford and bandmates Ben Lovett, Ted Dwane and Winston Marshall discover their love for American roots music. It started with the "O Brother, Where Art Thou?" soundtrack. Harris appeared with Gillian Welch and Alison Krauss on the memorable song "Didn't Leave Nobody but the Baby." That eventually led them to the Old Crow Medicine Show and then deep immersion in old-timey sounds from America's long-neglected past.
They ran across Harris' imprint many times along the way, and with the help of dobro master Jerry Douglas, they help explore that legacy on the show.
"Pretty much every song that Emmylou has sung on is my favorite song of whichever artist she sang with," Mumford said. "I'm like an obsessive Emmylou Harris freak and I'm not ashamed."
In turn, the quartet has helped shine a light on the influence Harris and the extensive roots underground still exerts. The band, which released their new album, "Babel," Tuesday, were a growing success story in that community when they appeared on the 2011 Grammy Awards with Bob Dylan and the Avett Brothers, launching Mumford & Sons into the national popular consciousness. Their album "Sigh No More" is now double platinum, and "Babel" is one of the year's most-anticipated albums.
"For us, it's kind of a bit of a dream come true," Dwane said. "We'd never thought we'd get to travel so extensively, meet our heroes and collaborate with so many people. ... We're just having a really nice time."
Like the band, fans have discovered something new in those old sounds. Mumford & Sons routinely drew 10,000 and more fans on their Gentleman of the Road tour across the U.S. this summer, almost all of them dancing along to Marshall's banjo.
"Folk music has always been there, but it's wonderful to see the infusion of freshness and energy, but still having that passion," Harris said. "Not just mimicking what went before, but infusing it. I was joking about the banjo, but I'm serious."