Nate Ruess of fun. (left) and Will Noon perform at DAR Constitution Hall in Washington, D.C. The band is still riding high off of the success of their sophomore album "Some Nights.” (Kyle Gustafson/FOR THE WASHINGTON POST)

A weird but mightily enthused jumble of demographic data points gathered at a sold-out DAR Constitution Hall on Thursday night, equal parts post-work 20- and 30-somethings, under-18s out on a school night, and grown-ups of parental chaperoning age — some of whom, notably, didn’t bring the kids.

What force of nature brought all these generations together in hand-clapping exultation? That would be fun., a New York-based group that’s currently riding high with six Grammy nominations, including nods in the four top categories — record of the year, song of the year, album of the year and best new artist. The band’s music is edgy enough for young indie fans, earnest and catchy enough for their teeny-bopping little sisters and usually tame enough for their parents, too. It’s a combination that has helped fun. emerge as the rare new rock act with total crossover appeal — something the band doesn’t seem to be quite at peace with.

When fun.’s magnetic frontman, Nate Ruess, a giddy 30-year-old with a voice like Freddie Mercury’s and a face that looks to be forged from the likenesses of every handsome, white male box-office star of the past decade, burst onstage in a slim-fitting patterned short-sleeve shirt buttoned up to his neck, it looked like a stroke of mass-marketing genius. To those his own age and younger, he was the picture of cool, smirking prep-school mockery, while to many of their elders, he looked peppy and clean-cut enough to have just stepped off the stage of “The Book of Mormon.” Catapulting into “Out on the Town” and the bouncy, Queen-emulating “Some Nights,” he proceeded to teach a master class in how to work a crowd.

Fashioned from the broken pieces of indie outfit the Format, Ruess and his bandmates released their quirky, acclaimed first album, “Aim and Ignite,” in 2009 before striking gold last year (and platinum just a few weeks ago) with their absurdly singalong-able second album, the sometimes-jubilant and sometimes-bummed-out invincibility-of-youth opus “Some Nights.” After a “Glee” cover and a juicy spot in a Chevrolet Super Bowl ad, lead single “We Are Young” rocketed up the Billboard Hot 100 chart and held the top spot for six straight weeks. Fun. was firmly planted in the mainstream, whether the band liked it or not.

For two-thirds of the show, the band mostly behaved like the adult-pop-radio act it is now, intentionally or otherwise, is. Tom-toms boomed and guitars wailed, but never too belligerently. Doleful puppy-eyed gazes, Mick Jagger pouts and dazzling Crest Whitestrip grins radiated to every corner of the auditorium as Ruess paraded around the stage, gold-topped microphone in hand.

Nate Ruess and Andrew Dost of fun. perform at DAR Constitution Hall in Washington, D.C. (Kyle Gustafson/FOR THE WASHINGTON POST)

But when the set reached the profanity-strewn breakup anthem “What the [Expletive],” some parents began pursing their lips; a few family jam-outs silently screeched to a halt. And after Ruess kicked off the aggressive “One Foot” with an “Aw, [expletive]!,” he bounded up from the side stage into the balcony-level seats. Families near him suddenly looked a little alarmed.

Fun. finished prettily with a soft, twinkling-light display accompanying the heartfelt “Stars.” But Ruess and company had made it clear — fun. was no sellout to the family-friendly mainstream. At least not this night.

Fetters is a freelance writer.