Gnarls Barkley had the success of their debut 'St. Elsewhere' sewn up before it was even released - spawning a multi-million selling single ('Crazy') will do that for an album. This time around, however, it's a different story for Brian 'DangerMouse' Burton and Cee-Lo Green: the self-designated Odd Couple have no chart-dominating single to prime them for a repeated success.

It's not really surprising, once you've heard The Odd Couple in its entirety. Unlike its predecessor, this is an album low on high-spirits and high on anxiety medication; gone is the celebratory warmth that coated St. Elsewhere, in its place is a sense of claustrophobic melancholy, overwhelming seriousness and bleak, suffocating arrangements. Whether it's an indication of either of the duo's personal circumstances is, of course, purely speculative - perhaps they just got tired of the handclaps and soulful stomps.

Though Green's voice is as robust as ever, the music that soundtracks them is at times unrelentingly glum. Open Book, for example, scatters a messy drum beat across an fire-and-brimstone score; Would Be Killer's jittery, time-shifting soundtrack is as sinister as if Green himself was the Child Snatcher from Chitty Chitty Bang Bang, and No Time Soon's gospel tone is shattered by a futuristic barrage of beats and samples.

Having said that, it wouldn't be a Gnarls Barkley album without at least some reprieve from the solemnity. Blind Mary, Neighbors and Surprise are all likeable numbers that open up the album and break the tension that's at times, difficult to listen to. The Odd Couple is a tougher proposition than most fans will expect, but it's by no means the worse for it. Just don't choose it as your party soundtrack.