Wild scenes at the Barbican. In the centre of the stage is a hefty-looking guitarist in a straw hat and a shirt that would impress Nelson Mandela; he is improvising a furious blues that contains echoes of a whole batch of songs, from Muddy Waters through to Howlin' Wolf, though the Wolf seems to have mysteriously migrated from Chicago to northern Africa. The backing is provided by Tamashek musicians, wearing long robes and headscarves, who add in their own sturdy and wailing guitar riffs, drumming and hand-claps.

Then one of the robed figures starts singing; others dance across the stage and the bluesman begins to follow their hypnotic, insistent beat. Taj Mahal has teamed up with Tinariwen from the deserts of northern Mali, and though they only met for the first time the previous day, the result is spectacular.

This is, of course, nothing new in the African blues. Ry Cooder has worked with Ali Farka Toure, and Taj Mahal recorded a notable album with another Malian, the kora player Toumani Diabate. These were stirring but delicate sets - nothing like this spontaneous, furious and exhilarating work-out. Tinariwen had not even heard of Taj Mahal until soon before this event, but they share what is called "assouf", the sense of pain and loss that is central to their rhythmic and compelling blend of desert blues.

Tinariwen started the show with a rousing set in which they were joined by the classy guitarist Justin Adams; it promised well for their festival appearances later this summer. Then on came Taj Mahal, backed only by drums and bass. He changed styles frequently, but concentrated on the lilting, easygoing country-blues with which he established his reputation back in the 1960s. On Corrina he demonstrated his slinky guitar and vocals work, while an upbeat Blues Ain't Nothing showed off his driving dance style (and skills at mimicry). It had been an impressive concert, but that final collaboration made it memorable.