Sweating in the desert sun at the recent Coachella Valley Music and Arts Festival in Indio, Calif., singer Cee-Lo Green points to a word tattooed on the side of his shiny, bald head.

" 'TRILL,' " he says, grinning. " 'True and real.' "

It's an appropriate catchphrase for hip-hop gospel troupe Gnarls Barkley: the unlikely pairing of DJ and producer Danger Mouse (Brian Burton) and Green (Thomas Calloway).

Their hit debut album, "St. Elsewhere," reeks of pure stripped-back soul.

Like fellow genre-benders Outkast, Gnarls Barkley's combo of psychedelic rumblings, earnest lyrics and poppy funk has cemented its spring-to-summer success.

In April, the band's bass-heavy single, "Crazy," topped the British singles chart as the first track to reach No. 1 based on computer- download sales alone.

Since its U.S. release May 9, "St. Elsewhere" has shot up into the top 20 of the Billboard charts.

"None of this was really preplanned," Burton says, lounging next to Calloway. "It just happened. It's taken a couple of years to make the record, and it's all organic."

Calloway, a member of Atlanta hip-hop's Goodie Mob and the rap collective Dungeon Family, had forayed into his own brand of scratchy-voiced soul -- somewhere between Screamin' Jay Hawkins and Al Green.

Burton -- who gained fame for "The Grey Album," a mash-up of Jay-Z and the Beatles, and later worked with Gorillaz -- enlisted Calloway in 2003 for a remix for Danger Mouse's "Ghetto Pop Life" album with rapper Jemini.

A musical merger was born.

"We were just trying to impress each other," Burton says of their ensuing correspondence, which involved the two working in an Atlanta studio and sending snippets of tracks back and forth.

The result turned out happily chaotic, from fun, thumping tunes such as "Go-Go Gadget Gospel" to the darkly witty "Necromancer" to frank odes like "Just a Thought."

In person, Burton and Calloway couldn't look and act less alike -- yet their odd coupling works as a magnet, drawing the other in.

Burton, wearing shades, is slender and matter-of-fact. Calloway, in a white tank top, with tattoos covering his arms, is heavyset and philosophical.

Onstage and in photo spreads, the pair eschew casual clothes for costumes as part of their Gnarls Barkley identity.

They've appeared as the hoodlums of Stanley Kubrick's thriller "A Clockwork Orange," as the metalheads of "Wayne's World" and the nerds from "Napoleon Dynamite."

At Coachella, the band's first scheduled U.S. appearance, an all-out "Wizard of Oz" theme dominates, with Calloway sporting a red curly mane and sweeping yellow, white and red robe as the Lion.

Burton, tucked away behind a turntable, gleams silvery as the Tin Man.

A guitarist and bassist in green face paint are the Wicked Witches of the West, while backup singers are dressed as the Scarecrow and Dorothy.

About halfway through the set, Calloway strips down to baggy shorts and a T-shirt reading "Mean Ol' Lion." He commands the stage, raising his fists as the kids in the audience go wild.

"Why would anyone want to take a picture of me in my jeans and T-shirt, just there?" Burton asks. "I feel much more comfortable if I'm wearing something silly. I would take a picture, too, if I saw someone looking like that."

Calloway has a more tongue-in-cheek take on the matter.

"I promise, it's just good, clean fun," he says. "It's an extension of our personal taste, a way of showing humility. Don't take anything too seriously. Have fun; open up your mind."