The rise of lower-case pop band fun has been one of those surprising success stories that suggest that, while the music industry as we once knew it is dead, stars are still being born. Four years ago, no one had the trio of Nate Ruess, Andrew Dost, and Jack Antonoff earmarked for stardom, as the band’s debut disc was not exactly torpedoing Lady Gaga or Katy Perry off the charts.

How things have changed, with the band’s 2012 sophomore album, Some Nights, eventually becoming perhaps the biggest sleeper of last year. Thanks to a slew of smash-hit singles—including “Some Nights” and the inescapable “We Are Young”—fun is now officially an It Band in the grandest sense of the term. You want impressive? How about the fact that fun was the first rock group to debut at number one on the Billboard charts since Nickelback, who pulled off the feat with “How You Remind Me” in late 2001?

Forget building a bit of buzz on Gorilla Vs. Pitchgum. Fun has managed the most difficult trick in niche-fractured modern pop music: cracking the mainstream and reeling in a mass audience. Instead of playing small and intimate clubs on its current North American tour, fun is packing the kind of venues that make you glad someone invented the Jumbotron.

If this has gone to the heads of the band’s three members, it certainly doesn’t show when the Straight tracks down Dost after a sound check at Denver, Colorado’s iconic Red Rocks amphitheatre. The down-to-earth musician has plans for the afternoon, and they don’t involve hunkering down in a strip club, scoring a bag of Colombia’s finest powdered export, or throwing flat-screen televisions into swimming pools.

“Things are going really well for us right now,” Dost says, “but all I’m thinking about right now is what I’m going to eat for dinner, and whether or not I should shower again because I’m really sweaty. Those are the kind of things that sort of come up on a daily basis, and I suppose that’s good. The sweatier you are, the more grounded you are as a general rule.”

Credit his levelheadedness partly to having had less than lofty expectations for Some Nights.

“We thought we’d made a record that we could be proud of,” the multi-instrumentalist says. “But I don’t think there was any way that we could have foreseen everything that has happened over the past couple of years. We kind of felt the same way we did after making our first album. We thought that all you can really do as an artist is make a record that you yourself really like. After that, it’s all out of your hands.”

Some Nights didn’t exactly rocket off the starting line, which might have had something to do with the fact that pigeonholing the record isn’t easy. That reality raises the question of who precisely the target audience is. The band members start out by celebrating their inner Freddie Mercury fans on “Some Nights Intro” (witness the fit-for-a-Queen vocals and audacious opera breakdown) and then prove equally skilled at Fab Four pop in “All Alone” and Jackson 5–brand candied soul in “Stars”.

Along the way, there’s no shortage of experimenting. The songs burst with symphonic strings, harpsichord, and choirs that make you wonder if fun has spent a night or two studying the collected works of the Polyphonic Spree.

It’s all a leap forward from Aim and Ignite, which got the group pegged as a progressive-pop group in the vein of Panic! at the Disco (who, incidentally, released a joint single with fun back in 2011).

The shift in fun’s sound has something to do with the band members channelling their inner hip-hop heads. Dost is a huge fan of the genre, even if it took him a while to fully appreciate it.

“Growing up, I was all about the Beatles and a lot of pop-punk stuff,” he says. “From there, I moved into classical music and started getting more into that as a classically trained trumpet player. Hip-hop didn’t come until much later. It was in college that I started to get really into it, developing a pretty deep love for it.”

That love—along with an undying admiration for Kanye West’s My Beautiful Dark Twisted Fantasy—would lead fun to approach and then catch the attention of producer Jeff Bhasker. In addition to West, Bhasker has worked with Beyoncé, Drake, Jay-Z, and countless other heavy hitters.

“It was so nice to work with someone from a world that we were kind of unfamiliar with beforehand,” Dost offers. “He’s from a world where people make beats, which is something I’d never really considered doing before.”

Bhasker can take part of the credit for the fact that the organic drums of Aim and Ignite are nowhere to be found on Some Nights, replaced by preprogrammed percussion and loops.

“One of the most exciting things of making this album was that it was a real learning process for all of us,” Dost says. “We were all fired up and learning from each other, and also from our producer, Jeff. It was a huge time of growth, but also of becoming more confident of who we are as a band, and also as individual songwriters. It was like ‘Here is what I can do, here is what you can do—let’s combine it all and make something better than any of us could do on our own.’ ”

Even though he’s now a Grammy-winning musician with a platinum record, Doss says this with complete humility. In fact, he comes off as completely genuine when he suggests that all he really wants at this point in his instant-celebrity life is a shower.