The audience yells along with Jenny Lewis’ impassioned NAF at the Troubadour

The setup at the Troubadour Monday looked like a post-prom house party.

Columns of balloons were tied to the rafters, and the stage was full of young people bopping to a DJ’s disco tracks. A homemade peace sign lighted up a little drum-bass-synthesizer rig in the middle of the floor, where the band would soon play right in the thick of the crowd.

The group even had a sarcastic-teenagery name: Let’s just call the act NAF, as the full name bawdily implies that its three members are superlatively genial (the ‘N’ stands for “nice”).

From all that, NAF seems like quite the dashed-off act to be headlining two sold-out gigs at the Troubadour on Monday night. But the band is a new project from Jenny Lewis, one of L.A.’s finest folk-rock singer-songwriters, and two indie-veteran friends, Erika Forster of Au Revoir Simone and Tennessee Thomas, best known for her work with the Like.

It’s the most freewheeling thing Lewis has ever done in her career. But that doesn’t mean it’s without sharp edges.

When the trio descended in matching army jackets, black berets and T-shirts the group was selling at its merch table, the massed crowds snapped right in line around them. The group’s sound strips punk and funk back to the essentials -- a rhythm section, some vocal echo and a little bit of synthesizer. It harks back to the best stuff of the late ’70s, right when punk was being rebuilt -- Tom Tom Club, Bush Tetras, Public Image Ltd.

Jenny Lewis, center, performs with drummer Tennessee Thomas and bassist Erika Forster.

(Luis Sinco/Los Angeles Times )

Anyone familiar with the musicians’ other bands might have been a bit surprised to find such a strong influence from that era. But it turns out that the act’s militaristic dub-punk can be funny, with real feeling. Nice, even.

Most of the band’s tunes -- “Runaway,” “Angel,” “Higher” -- were less than three minutes long, and usually little more than a bass line and a chanted chorus, spiked with heavily reverbed yelps. Though the album was a surprise release, many in the crowd already knew the lyrics. Lewis, after all, commands an army of super-fans, and this was an easy record to yell along to.

Some of the songs were laugh-out-out witty: “Cookie Lips,” with an unprintable hook, is one of Lewis’ best good-riddance-to-bad-dudes tunes.

But at the moments when Lewis cut through the spacey dub echoes with her brassy voice, it was obvious that’s she’s not just one of our city’s great vocal talents, she’s owns one of its most vivid imaginations as well.

The show ended on two striking notes. The first was the band’s most talked-about single, “Guns,” a plainspoken plea to de-escalate conflict that’s taken on a more literal poignancy. “I don’t want to be afraid / Put your guns away,” Lewis sang.

Other artists, especially the current generation of Black Lives Matter-affiliated rappers and soul ringers, have made that point more eloquently. But it’s never been more necessary to hear a venue -- any venue -- full of young people singing about their fear, as well as their desire for disarming America right now.

Then NAF closed with a minute-long, self-effacing song that bid adieu to everyone who clamored into the Troubadour for this weird, delightful little show. “We’re nice as … . Wish you good luck,” they yelled.

A half-hour after it started, it was all over. Everyone left feeling a bit luckier for it.

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