Considering John C. Reilly sang in “Chicago” and “Walk Hard” and rapped in “Step Brothers,” it shouldn’t come as too much of a surprise that he makes music on the side. The actor, 49, has been touring and playing festivals the past several years with his group John Reilly and Friends, yet the only music he’s released is a pair of 7-inch singles produced by Jack White in 2011. “We’re kind of deliberately obscure at this point,” Reilly says. The “we” are musicians Becky Stark and Tom Brosseau, who’ll join the singer-guitarist onstage at Sixth and I on Tuesday to play covers of old folk songs by The Delmore Brothers, Ray Price and more.

What made you want to pursue folk music?
It was something I was already doing in private. It’s one thing to listen to this music recorded, but it’s a whole other experience to share it in a room with everybody. I think that’s how music stays alive.

The way we pick the setlist for the show is eternal melodies — songs that you hear one time and you’re like, “I already have that song committed to memory.” I’m not doing it to get any more famous, certainly.

You do it because you love it.
I also like to shine the light on these people that I play with because, sometimes, it can be tough to get people to show up for shows. Throw my name up there and if that gets them in the door and they think they’re going to see a “Step Brothers” revue then so be it. We give them a night of folk music and bluegrass music and they end up walking out feeling really good.

So even if people don’t know the songs, they’re going to leave liking them?
It’s songs from the roots of the tree of music. There’s a reason they feel familiar, because they’re deep in there.

Is that what draws you to them?
I don’t know. That’s one of the interesting things about doing this music and seeing what music ends up coming to you. Why do certain songs survive? Why did “Happy Birthday” become the song that everyone knows.

There must be something about the structure of those notes. Or “Auld Lang Syne,” these songs that are a permanent part of our psyche. Were there songs in the past that people thought were a permanent part of their psyche and now are forgotten? In our age, permanence is a rare thing.

Do you write songs?
I write songs, but we don’t perform any original music with this group. But who knows, maybe we will. If I can ever write a song like “Auld Lang Syne,” maybe. Not that we do “Auld Lang Syne.”

What do you get out of performing live?
I grew up doing theater and I do a lot of comedy stuff. I think it’s just in my blood, you know? Being able to be onstage and connect directly with an audience is really what I do. I’ve made a very nice living making films but I think my basic skill set is meant to be in front of an audience.

It seems that you’re yourself onstage. Is that part of the appeal?
There were a little bit of growing pains when I first started doing it because I was so used to being able to hide behind a character, so I do like that. There’s this sort of bracing honesty and there’s a sincerity to the music and I’m not pretending to be something else.

There’s nothing to hide behind.
Yeah, and we’re singing around one microphone, we don’t have earpieces in, we’re not blasting you with an enormous sound system. What you hear is what we have.

Is the kind of music you play also the kind of music you listen to?
Yeah, I rarely listen to anything other than stuff pre-1968, in terms of stuff for the band. But I still have really eclectic musical tastes. I’m a big fan of Fleet Foxes and, believe it or not, I’m a huge hip-hop fan. I listen to a lot of hip-hop in the car.

Do you see yourself pulling back on acting and going full-on into music?
I don’t think I would ever deliberately pull back on acting. I try to just follow the river. Whichever way the current is going, that’s the best way to go, and music has been creeping in more and more as I go along. Hopefully, I never have to give up anything in order to keep doing fun stuff.

Folks and friends

For the John Reilly and Friends show at Sixth and I, the actor will be joined by frequent collaborators Becky Stark and Tom Brosseau. “What really brought the group into existence is a shared love of this music,” Reilly says. Stark fronts the eclectic band Lavender Diamond and has been singing folk music since she was a kid. Singer-guitarist Brosseau performs as a solo artist — his latest album, “Grass Punks,” came out last year — as well as with the groups American Folksingers and Les Shelleys. Both Stark and Brosseau have acting experience, though not as much as Reilly.

Sixth and I Historic Synagogue, 600 I St. NW; Tue., 8 p.m., $25-$30.

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