The stickiest whistling of the 21st century was conceived in Sweden, nurtured in the collective musical subconscious of three Stockholm musicians, shaped by their distinct creative personalities and love of New Wave, alt rock and ’60s pop, and born several years later in a catchy, charming pop ditty, “Young Folks.”

By that time, Swedish trio Peter Bjorn and John — singer/guitarist Peter Morén, singer/bassist/keyboardist Bjorn Yttling and singer/drummer/percussionist John Eriksson — had enjoyed some minor fame, but still worked day jobs to support themselves. “Young Folks” was the first single off their third album, 2006’s Writer’s Block, and by mid-2007, the song seemed to be everywhere — sampled by Kanye West, covered by Pete Yorn, used in TV shows ranging from Grey’s Anatomy to Gossip Girl and in ads by Budweiser, Napster, American Eagle Outfitters and AT&T, among others.

“It changed everything,” de facto leader Peter Morén tells me from a hotel in Utah a few weeks ago in the midst of his band’s current gig opening for Depeche Mode. He says that up until that point, they did the band for fun. “But now we do the band for money and other stuff for fun… no, no, it’s still fun,” he laughs, adding, “It’s just not something that we really expected.”