At about 11:30 p.m. on a Wednesday night in March, vocalist C.J. Edwards steps up to one of the five microphones set along the front of Dozen Street’s stage.

“When you’re taking every kind of pill,” he sings plaintively, introducing a motif, a variation on the 1977 Parliament joint, “Funkentelechy.” A guitarist on the stage follows him, picking up the riff. Then the drums kick in. Vocalists drift up to the other mics, their voices swirling in rich harmonies. Finally the bass drops, filling out the ensemble, and for the next ten minutes or so, the group unwinds an extended jam. The seasoned artists explore the familiar song, adding a rhythmic flourish here, inverting a melody there. They weave an engrossing tapestry of sound.

As the set progresses, the musicians offer their expertly harmonized takes on '90s R&B jam “Dancing Too Close” and Prince’s “Kiss,” but that Parliament track sets the perfect tone for the evening. Like George Clinton’s band of free-wheeling funk-a-teers, the Butter N Jam crew (they call the band 12th and Chicon) take a daring musical approach that’s both experimental and engaging. They embrace complexity without sacrificing the body-rocking energy that makes you shake what your mama gave you.

They’ve been hosting this weekly jam for almost five years, and in that time, it’s grown to be Austin’s nucleus for groove theory, a place where the city’s top hip-hop, funk and soul players flex their chops in an exhilarating meeting of musical minds.

If you like your grooves funky, your harmonies tight and your favorite jams deconstructed: “It started out as a night for musicians who do soul music and hip-hop to sort of have a little nexus to come together in the middle of the week when we’re not doing our cover band gigs, to vibe with each other,” says vocalist C.J. Edwards, who worked with club owner Madi Distefano and guitarist Dave Manley (who has since left Austin) to help “found the feast.”

Edwards calls it a “vibe night.” The cast shifts from week to week, but some of the city’s in-demand side players are usually in the mix. Special guests and featured artists also sit in and each evening unfolds as a sprawling jam.

“I wouldn’t say it’s all improvised, but we don’t know what we’re going to do,” Edwards says.

» RELATED: Margaret Wright has a smile for your soul at her Skylark Lounge residency

The group uses audio cues to communicate.

“We know if we hear a certain line, ‘Superstition’ is going to come up, but we play with it. It’s not the same ‘Superstition’ every time,” he says.

Gorgeous four- to five-part vocal harmonies distinguish the event from other jam sessions. A love for that style of singing came early to Edwards, who was raised in the Church of Christ.

“We didn’t really have instruments in our church, and we didn’t have a choir, per se. Everybody in the congregation sang. So you had to learn how to sing harmony and it sort of becomes second nature,” he says.

Featured artists sometimes include prominent local names like Kydd Jones, Bavu Blakes and Riders Against the Storm, but Edwards says they focus on “really trying to get the crowd involved and to get people who are not necessarily pros at singing or rapping yet” onstage.

“It’s kind of like an open jam,” he says. But there’s a caveat: “Come on, if you can do it, do it, but if you’re wack, we will kick you off,” he says with a laugh.

The sound: The group began as an avant garde outfit that leaned toward a jazzy sound, but under the musical direction of keyboard player Jonathan Deas, their core sound has drifted to more of a '90s R&B and neo-soul flavor. When Deas, who is currently touring with Gary Clark Jr., is out of town, Dwayne “D Madness” Jackson slides into the director’s chair. “Then it gets real funky,” Edwards says.

Either way, you’ll hear recognizable riffs torn apart and built back up in unexpected and delightful ways.

The vibe: The space has a feel that’s equal parts dive bar and D.I.Y. art space. An ornate mosaic of a peacock created by Distefano’s sister, Stefanie Distefano, adorns a wall near the bar where friendly mixologists serve a variety of custom cocktails along with wells, brews and wine. Across the room, acoustic tiles wrapped with the remnants of vintage leather jackets create a patchwork wall covering. The crowd is diverse and welcoming. There’s a lounge area with a pool table and ample seating near the entrance and a spacious patio out back. There are a few tables and stools scattered through the club, but the stagefront area is mostly open. This is a dance party, friends.

The core players: Myke J, Anthony “Duece” Monroe, Reggie Coby, C.J. Edwards (vocals); Darius Jackson (guitar); Dwayne “D Madness” Jackson (bass); Jonathan Deas (keyboards); Mario “Meo Soul” Craft (drums); Danny “Dread” Thompson, Chandra Washington (percussion)

C.J. Edwards says: "Come with an open mind because we’re going to sing songs that sound familiar, but we’re gonna play with them, so don’t get mad at us for messing up your lyrics when we play the song. And just come with the heart and the warmth to have fun. That’s all we’re doing. We’re just having fun. We’re just trying to bring joy. A lot of people feel like it’s church, and I really appreciate that. ... All I wanted to do when I went to church, like when I was a kid, was go sing. I wasn’t even really there for all the preaching ... but I remember how the singing made me feel. The congregation together, it was something very special, everybody is riding on that vibe."

Club owner Madi Distefano says: “They’re all gigging musicians so they’re all working all the time, but a lot of the time they’re backing bigger acts or touring acts or they’re playing weddings, and they don’t exactly get to do whatever the hell they want. So that’s what Butter N Jam was created for, and it became very special and very important to me and to the east side largely because of the diversity of the crowd and of the musicians. To me that represented East Austin. I was very conscious of being a white woman opening a venue in a traditionally black neighborhood, and I very much wanted black residents and musicians, and also Latina, lesbian and gay and everyone, I wanted to make sure people felt welcome to come to that venue that’s been there for 100 years in different incarnations.”

If you go: The bar (1808 E. 12th St.) takes a “pay what you can afford” approach to cover for the event. Distefano says patrons drop anything from pocket change to $20 in the bucket, but the average tends to be between $3-$5. Free parking is available on the street and in the lot on the southeast corner of 12th and Chicon streets. The Butter N Jam sessions don’t start until 11:30 p.m., but show up early for the D Madness project mixing up funk, reggae and soul grooves.