Sigur Ros is Funnier Than You Think.

From left: Georg Holm, Kjartan Sveinsson, Jonsi, Orri Pall Dyrason. Photo by Lilja Birgisdottir

Sigur Ros's frontman, Jon "Jonsi" Thor Birgisson, is reminiscing about Donna Summer.

"We were in a tour bus and one of our members was getting married in Las Vegas," he recalls, "and I was dressed in a Three Musketeers costume, dancing to the 17-minute version of 'Love to Love You Baby.' "

If the image of Birgisson -- he of the cooing falsetto -- slinking about to the late disco queen's naughtiest track seems out of character, we argue that that's only because you've been taking Sigur Ros for a bunch of self-serious, musically long-winded softies for far too long.

We know, we know. For the past decade and a half, the Icelandic quartet has performed slow-building, high-drama arias, many of which rarely clock in at fewer than six minutes. And yes, tuning into that sort of thing is a tall order in our A.D.D.-addled age. But if you ask us, these guys have a sense of humor--and never has it been more apparent than with their sixth LP, Valtari.

"When we started out, we had really high ideas about music," says Birgisson, who is gay. "But as you grow older, you learn to relax a little bit and enjoy things." Not buying it? Exhibit A: The group commissioned a dozen filmmakers, including John Cameron Mitchell and Ryan McGinley, to direct music videos for songs from Valtari, giving them carte blanche to be as literal or interpretive as they wanted. The first clip that surfaced, for the six-minute-and-fifteen-second (ahem) opening track, "Eg Anda" (directed by Ragnar Kjartansson), provided step-by-step instructions, spelled out on cue cards, on how to give someone the Heimlich maneuver. "It's totally out of our hands," Birgisson says of the project. (Watch the video for "Fjogur Piano" starring a full-front Shia LaBeouf here.)

As for the music itself, he refers to the record as "calm" and "introverted" and "soundscapey." He's totally right: It features a children's choir and twinkling, bell-like dulcitones, and the last three songs don't even have any words. But Valtari means "steamroller" in English. For a record this lulling and pretty and harmless? Now that's just plain cheeky.

Valtari(XL Recordings) is out now.