{shortcode-8d52eab11d65184a52a2267a476f80a9f1d76be3}The audience members at Friday, Sept. 7’s First Aid Kit concert were more buttoned-up than the throngs that sometimes fill Boston’s Blue Hills Bank Pavilion. The crowd filed into the theater decked out in tasteful scarves, ready to hear a band that matched their cleanliness — and like its audience, First Aid Kit avoided an overly saccharine performance primarily thanks to their genuine enthusiasm.

First Aid Kit, a band comprised of Swedish sisters Klara and Johanna Soderberg,is an indie-folk group that leans heavily on earnestness. After experiencing some burnout following their 2014 album “Stay Gold,” the sisters took a lengthy break. But between January’s breakup album “Ruins” and their current tour, First Aid Kit has fully reclaimed their acoustic guitars and gingham dresses. If they are still experiencing the exhaustion they reported in 2015, Friday’s concert made it impossible to tell.

First Aid Kit took the stage after opener Julia Jacklin, who set the tone for the night with a sweet, unaffected setlist. Jacklin skews more towards indie pop than First Aid Kit’s folksiness. With a slight genre shift, her vocal style would fit in on a track written for Alessia Cara. First Aid Kit’s aesthetic, however, is entirely its own. The sisters’ style is a kind of Swedish Americana kitsch — there were the gingham dresses, of course, and the trombone accompaniment, and the acoustic instrument selections. The background displays, however, were the single best example of First Aid Kit’s sentimentality. Styled like a Looney Tunes sketch from the ’50s, the animations crossed the screen in droves: Route 66 memorabilia backed “It’s a Shame,” a stained-glass sun rose behind “Stay Gold,” and a pack of wolves supported (naturally) “Wolf.” Two separate songs, “Master Pretender” and “Emmylou,” were set against a backdrop of black-and-white photos of the band.

The sisters themselves were physically static on stage, so the sets did most of the visual work. The animations had sufficient flair, however, so the performers’ lack of motion seemed both natural and fluid. If there had been a drop of cynicism throughout the performance, First Aid Kit would be easy to rip apart — but there wasn’t, and so it isn’t. Earnestness, after all, is First Aid Kit’s brand. They lie somewhere in between indie and country, twangy without being twee, showcasing their sisterhood and their sweetness without ever fully commercializing it.

The show became lackluster only when the band tried to escape these folksy parameters. A generic protest song for the #MeToo movement, for example, fell slightly flat: While it was topically powerful, the song fell outside of the band’s genre, and it showed. Angry protest just isn’t what First Aid Kit is about. Their audience clapped politely for the sisters’ anger, but they seemed happiest when the songs tended towards the bittersweet — when the listeners could sway back and forth in their ballet flats, silently mouthing all of the words.

The Soderberg sisters are powerful singers whose ranges are just as towering live as they are on recordings. They nail dissonant harmonies with so much confidence that the clashes sound obvious. They are talented enough that critics have been suggesting they’ll blow up for years — but First Aid Kit has been resolutely itself for long enough now that traditional mega-fame may never come. This isn’t a tragedy. It means that First Aid Kit can continue to sing folk songs exclusively to an audience that wants to hear them. This is a band that, with very few missteps, knows who it is. And for audience members who like the group’s brand of nostalgic country, First Aid Kit’s enthusiasm makes for a live performance that is both engaging and endlessly skillful.

—Staff writer Iris M. Lewis can be reached at at iris.lewis@thecrimson.com.