AUSTIN, Texas--Acclaimed producer Danger Mouse has brought his trademark sound over the years to the likes of the Gorillaz, the Good the Bad & the Queen and, of course, Gnarls Barkley.

The Black Keys' Dan Auerbach at SXSW.

On a sizzling afternoon here at South by Southwest (SXSW), hundreds of fans packed into La Zona Rosa to see just what he had cooked up with the second-most-popular two-person blues outfit on the planet, the Black Keys. The duo of guitarist/singer Dan Auerbach and drummer Patrick Carney is set to release its Danger Mouse-produced album, Attack and Release, on April 1.

Auerbach and Carney took the stage with an expanded setup, adding an electric organ and more effects pedals to its standard guitar-and-drums rig. They immediately broke into a scorching cover of Captain Beefheart's "Here I Am I Always Am," with its plea, "Yeah my heart is in your hand/please don't take my love in vain."

The duo revisited two of its older gems, "10 A.M. Automatic" and "Girl Is on My Mind" before unveiling its first new song, "Strange Times." The track was darker and more modern than anything the Keys have recorded to date. And it was far less accessible than the blues-soaked rock on which it has made its rep.

They followed it up with another new one, a fuzzy psychedelic soul track called "Oceans & Streams." The tune found Auerbach sitting behind an electric organ, pounding the keys with the fury he usually reserves for his axe.

All in all, it signaled a sonic departure for the duo into less straightforward dirty blues and more off-kilter hard rock--perhaps more interesting upon further digestion.