INDIO, Calif. (AP) - Sweating in the desert sun at the recent Coachella Valley Music and Arts Festival, 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 catch phrase for hip-hop gospel troupe Gnarls Barkley: the unlikely pairing of DJ and producer Danger Mouse (Brian Burton) and Green (real name Thomas Calloway).

While the two perform in various costumes (they also prefer being photographed in character), 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. It just happened," Burton says, lounging next to Calloway in an outdoor VIP tent at Coachella. "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 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 his 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 also sending snippets of tracks back and forth.

The final result turned out happily chaotic, from fun, thumping tunes such as Go-Go Gadget Gospel, with its squealing horns, to darkly witty Necromancer, and frank odes like Just a Thought, in which Calloway moans: "And I've tried/Everything but suicide/But it's crossed my mind."

A snappy cover of 1983's Gone Daddy Gone by rockers the Violent Femmes completed the eclectic picture.

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.

When asked about his influences, Calloway pauses, takes a bite of his hamburger, and says "no one in particular, and everyone at the same time," before naming Al Green, for one and Aerosmith's Steven Tyler, for two.

Onstage and in photo spreads, however, 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 back-up singers are dressed as the Scarecrow and Dorothy. A string quartet is costumed as evil monkeys with black wings.

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.

The Wicked Witches shimmy, the Dorothys croon and the Tin Man bounces his head to the beat.

"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 another, 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 yourself or us too seriously. Don't take anything too seriously. Have fun, open up your mind."