Headlining the Hollywood Bowl in July, Cee-Lo Green announced that he and Danger Mouse, his partner in the future-soul duo Gnarls Barkley, were "contractually obligated" to perform "Crazy," the worldwide smash from Gnarls' 2006 debut, "St. Elsewhere."

Green was presumably joking -- "Crazy" is such a powerful invention that it's hard to imagine that even its creators are tired of playing it.

There is, however, something slightly obligatory about the outfit's new six-track "Who's Gonna Save My Soul" EP, which features no fewer than four versions of the title cut.

The original, from this year's "The Odd Couple" album, is well worth hearing again: A post-Portishead space-blues jam, the song contains some of the frontman's finest, most deeply felt singing.

And hearing "Soul's" demo version (one of the EP's three alternate renditions) demonstrates how complete a vision Danger Mouse had for the song from the beginning; for a studio magician whose music embraces the unexpected, he evidently leaves little to chance.

Yet nothing much is revealed by an instrumental mix or by a live take taped for MTV, nor does a live version of "Neighbors," also from "Odd Couple," tell you anything you didn't already know about Gnarls Barkley.

The set's sole new track, "Mystery Man," flatters Danger Mouse's collection of vintage keyboards but not much else.

Hey, even geniuses phone it in once in a while.

-- Mikael Wood

Gnarls Barkley
"Who's Gonna Save My Soul"
Downtown/Atlantic
One and a half stars