A bluegrass band headlining a 3,500-seat venue? In Philadelphia, a market that historically has been to the genre as Eagles fans are to discretion and decorum?

Greensky Bluegrass, the veteran unit will hit the Met on Friday and is no stranger to similarly sized venues and larger — including the nearly 10,000-seat Red Rocks Amphitheatre outside Denver.

The quintet, which was formed in 2000 in Kalamazoo, Mich., features a traditional, all-acoustic, bluegrass lineup of guitar, mandolin, banjo, upright bass, and dobro — a guitar with a metal resonator played by pressing on the strings with a metallic slide.

“The thing about Greensky is that while they do incorporate bluegrass, they can rock, they can jam, and they have an infectious relationship with their fans during their shows,” said Bruce Warren, assistant station manager at WXPN-FM (88.5). “This is a band that knows how to play to the bleachers and can make a soaring banjo or mandolin solo sound like a stadium anthem.”

Villanova native/Episcopal Academy alum Anders Beck, who has played dobro in the group since 2007, agreed during a recent phone call from his Colorado home.

When asked about the band’s burgeoning popularity, Beck said, “I think the best way to [answer] it is, because there is nothing ‘pop’ about it, and because we’ve spent years playing 200 nights a year, we’ve grown this fan base one person at a time, and there’s nothing fake about it. It’s as real as it can possibly be.

“Because we come from a jam-band type of ethos and play a different set list every night, and take chances musically, it makes people want to come to multiple shows on a tour and tell their friends about it. I think it’s a word-of-mouth thing that has occurred, and I think because, musically, we’re not any one thing — it’s folk music, it’s songwriter music, jam band, sometimes it’s metal. It’s everything.

“But [bluegrass] is not what we do. We’re a rock-and-roll band that plays bluegrass instruments. Bluegrass is such a finite thing. Because you have a banjo and a mandolin, you’re supposed to do it a certain way or you’ll piss off some people. But we’ve always been ourselves.”

Interestingly, Beck, whose first name rhymes with wanders, explained Greensky Bluegrass has always been a somewhat schizophrenic operation. It has released six studio albums since 2004 that have emphasized original compositions, most of them written by mandolin-player/lead vocalist Paul Hoffman.

But it is also an electrifying live act whose dazzling improvisational flights and willingness to put its unique spin on a crazy-quilt of covers such as Prince’s “When Doves Cry,” “Space Oddity” by David Bowie, and “(I’ve Had) The Time of My Life” from Dirty Dancing, have helped it achieve royalty status in the “jam-band” universe.

According to Beck, those bluegrass-infused covers are yet another reason for Greensky’s ability to reach listeners who might otherwise steer clear of the rustic music with roots that stretch back to the people from Britain who settled in the American South in the 19th century. He said the group has used covers to “connect with people who didn’t know our band: ‘These guys like Prince? I like Prince. We have something in common.’

“Now we have probably hundreds of original songs. But we still do a couple covers a night. It keeps it fun for us.”

As for his band’s dual personality, Beck suggested that with All for Money, the band’s new album that hits the marketplace Jan. 18, the two distinct sides that comprise Greensky appear to have finally melded together.

“This album, we kind of went with the idea, ‘Let’s try to make an album kind of like a show, and not be afraid to make it weird,' ” he said.

Beck cited the track “Courage for the Road” as an example of the band’s new philosophy.

“Rather than [imply] the jam is gonna be there, we made the song 10 minutes and jammed it out,” he said. “We played it like we'd play it live.

“And the title track [has] a space section in it that even I was concerned … went too far. And I’m usually one of the guys telling [the band] to go farther.

“But I think it turned out pretty well.”

MUSIC

Greensky Bluegrass

8 p.m. Friday, The Met Philadelphia, 858 N. Broad St. $30, www.themetphilly.com.