If you asked the members of the band Wolf! — a New York-based trio made up of guitarist Scott Metzger, bassist Jon Shaw and drummer Taylor Floreth — to walk onstage with no songs and no plan, they wouldn’t flinch.
That’s because the band’s first gig played out almost exactly that way.

About six years ago, Metzger, Shaw and Floreth had a reputation as musicians who could back various singer-songwriters whenever they needed a band. One night, the three were scheduled to play with a local singer at a club in Brooklyn. There was only one problem: The show was about to start and the singer wasn’t there. Rather than cancel the gig (the club wouldn’t let them), they took the stage without a vocalist and just started, well, jamming.

“I remember Taylor said, ‘What are we gonna play?’ and I said, ‘I have no idea what we’re gonna play but we’re gonna play something,’ ” Metzger recalls. “So we walked out and we just made up a set of music for 90 minutes, and it went over great.”

Refined versions of at least three songs from that night — the soulful “All Dressed Up (Nowhere to Go),” the Roy Buchanan-inspired “Chuckles” and the earworm-y “Pork ’N Slaw” — are still in the instrumental band’s repertoire today.

“We all trust each other musically, but we’re also all coming from the same pool of liking music and there’s a lot of common ground there,” Metzger says, citing Booker T. and the MGs and the obscure ’70s instrumental band Stuff as major influences.

Now, after gigging mostly in New York since that first fateful show, Wolf! is making a push outside of the city, starting with a concert opening for bluegrass band Cabinet at the 9:30 Club on Friday.

“We’re trying to act like grown-ups, finally,” says Metzger, 40. “And get out of the city more.”

Wolf!’s two albums — 2015’s self-titled set and last year’s “1-800-WOLF!” — feature short instrumentals that fuse surf rock, jazz and funk. In concert, the band opens up those compositions, deconstructing them and improvising around the main themes.

The clean tone from Metzger’s Telecaster-style guitar is key to the band’s sound — he’s doing most of the work when it comes to the melodies and the soloing — but Wolf! functions as a cohesive unit.

“We’ve been talking a lot more lately about the old Sonny Rollins trios, which were just bass, drums and saxophone,” Metzger says. “This was a really groundbreaking thing at the time, when he stopped using a piano. It was just three guys and everyone had to get really involved. Everybody had to be putting musical ideas out: the drummer, the bass player and the melodic instrument. If there’s just three of you and you’re playing 2 1/2 hours, you can’t just be a drummer sitting back there keeping time and a guitar player soloing all night.”

When it comes to writing songs, it’s Metzger — who has backed Anders Osborne and Amy Helm and has played in such bands as Joe Russo’s Almost Dead and RANA — who tends to start that musical conversation.

“I’m always sort of collecting ideas on my own and recording little demos — 30-second snippets of ideas — and I’ll bring those [to the] studio,” he says. “If anyone is feeling one of them, we’ll look into it and then some become songs and some of them become things that never happen again.”

The band is currently working on tracks for a third album.

“It’s certainly a similar vein ­— it may be a little bit smarter, maybe, a little bit more arranged,” he says, comparing the sound to the first two albums. “I think the looseness is always gonna be there because that’s the fun of [our music], and that’s what lets it breathe and sort of be a living thing.”

Metzger and bandmate Shaw can sing (Metzger occasionally covers The Band’s “Ophelia” during live sets) but he doesn’t see Wolf! ever turning into a band with lyrics.

“That’s not the spirit of Wolf!,” Metzger says. “Wolf! is an instrumental thing.”

9:30 Club, 815 V St. NW; Fri., 7 p.m.,$18.

UPDATE: Wolf will return to D.C. to play Gypsy Sally’s in Georgetown on Friday, March 2. Tickets are available here