In a world where it's the norm to have a one-off collaboration between a producer and a rapper, something special has to happen to prompt a sequel.

Of course, "Crazy" was all the prompting needed for Cee-Lo and Danger Mouse to rejuvenate Gnarls Barkley, their collaboration by mail that sparked the brightest and catchiest single since OutKast's "Hey Ya." But fans and critics have to understand that these two were exactly the types to walk away from a follow-up simply for the purpose of a cash-in, which makes that follow-up, The Odd Couple, such a strange proposition -- it's exactly like St.

Elsewhere, and fails to reveal a single new thing.

All the hallmarks of a follow-up record are here -- similar sounds and themes, for sure, but also a clear lack of innovation, lyrical and production touches that have since become clichés, and more than just a few passages that will prompt a severe case of listener déjà vu.

(Of course, many listeners may enjoy that sense of déjà vu.) As before, Danger Mouse's productions are miniature, modernist spaghetti Westerns, very closely detailed whether their major voice is an acoustic guitar or a choir of unholy voices.

These are then chained to amped-up beats and beefed-up basslines to create something that sounds both vintage and up to date, all at the same time.

Cee-Lo's lyrics and vocals again reveal a lunatic (or seer) who's occasionally more lucid than the sane, an enlightened psychopath wrestling with his demons and revealing the thin line between being crazy and sensible.

At times, The Odd Couple is a more beautiful record than its predecessor -- the duo has never put out anything more moving on a musical and emotional level than "Who's Going to Save My Soul," and Danger Mouse's production work outshines St.

Elsewhere on one track ("Open Book").

But all too often Cee-Lo relies on the same sort of lyrical cipher as on St.

Elsewhere, although none of them are as effective.

"I don't understand how I'm so understanding"; "I'm goin' on, and I think they'll have a place for you too"; "I could be a would-be killer" -- these are the ramblings of a madman; they may sound deep and profound late at night, but they're revealed as nonsense with the light of day.