Africa Express, Olympia, Liverpool

A vibrant celebration of African music on the Mersey

The Olympia, a one-time dance and variety hall, can rarely have seen the array of talent Damon Albarn and friends brought to it tonight. Ever since Live 8's organisers decided to stage a concert to "end poverty" in Africa without inviting the continent's musicians, Albarn has been countering the idea that it is a pitiful charity case with a series of direct musical actions.

Africa Express is an initiative that has taken mostly British rock musicians to Mali and the Congo, and African musicians to Glastonbury, Brixton and, now, Liverpool. The spirit has been one of open, intimate collaboration. Last night's staggering all-star, intercontinental line-up may be planting seeds more vibrant and profound than anything Albarn has done before.

The crowd is a mix of the committed and curious, who see massed drums followed by Amadou and Mariam. Amadou's silver guitar is soon streaming Africa-inflected blues riffs, but the couple from Mali look lost as The Magic Numbers jerkily intercede. For a moment, the Africa Express seems set to crash. But then the Afrobeat originator Tony Allen's drums gently roll everyone back into their groove, Mariam's pragmatic, soulful voice rides the brass section, and we're away.

Hard-Fi define tonight's possibilities. The west London ska of "We Need Love" is given an added blues riff by Amadou, barely noticed at the back of the stage. Then Rachid Taha, the Algerian-French king of rebel rai, dressed and moving like a Forties Casbah gangster, struts on. Taha's band help Hard-Fi turn "Suburban Knights" into north African trance. Richard Archer, usually the star, defers almost entirely to Taha's unruly energy, as he sings The Cure's "Killing an Arab" in Arabic, its meaning made hopelessly unstable.

Archer humbly confesses to me later that Hard-Fi's collaborators were "lowering themselves to be on the same stage as us". But his band have bravely opened themselves up to the most exacting, exciting music they've played; suddenly, you can hear new spaces and possibilities. Albarn and Africa have freed them. The sharp-suited Senegalese guitarist Wasis Diop, minus any Western stars, is treated as intermission music at first. But his light, long-rolling, effortlessly even rhythms become mesmeric. A second guitarist blurs styles from African palm-wine to the glistening lap-steel of a Southern bar band between dances, as Diop huskily sketches songs over the top: Senegalese sounds by way of Memphis.

You can't take the ego out of Reverend and the Makers' scattergun Northern rebel groove. But the stage soon fills, with a white-bearded percussionist in what looks like a medieval Mongol helmet and, most notably, Malian stars Bassekou Kouyate and his wife Amy Sacko. Kouyate at first struggles to find a spot for his ngoni (a lute-like instrument). But he eventually takes the unlikely lead on a crunching electric Chicago blues, sprinkling high, oriental-sounding notes. Sacko lifts her eyes to the roof with worldly wryness as she starts to sing. Soon, Baaba Maal, perhaps Africa's biggest star, is beside her, scaling notes and declaiming; she shoots a tough, take-no-prisoners ululation back. Amadou has returned, too, with virtuoso noir riffs. Solos are passed smiling down the line, as the reality of these disparate African peers uniting sets in. Kouyate, dressed in princely white robes on-stage, stands in a green parka in the crowd, watching. With the backstage drinks rider exhausted in seconds, "stars" have been mingling at the public bars all night. Celebrity has been cancelled.

Turin Brakes provide well-meaning, mediocre histrionics. Then Franz Ferdinand and Maal combine on "Take Me Out", the Afrobeat roots of Glasgow pop, so evident with Orange Juice, at last made utterly explicit. Kouyate and the London rapper Kano pile in, making Franz rougher and rawer. Like Hard-Fi, they are forgetting the Western pop industry's rules, and being reborn as musicians. And who knows what Maal is learning?

There are some middling soul-jazz jams, a nervous Get Cape. Wear Cape. Fly, and Elmore Judd, enlivened by Sacko's singing. Maal and Albarn each finally take centre-stage, the latter's frail cockney voice colliding with Kano's smart London raps. But it's Taha who waltzes on at 3am to steal the show. "Rock The Kasbah", with Albarn and Maal on board, is a pure riot.

Over accelerating, percussive brass, Taha grinds, dances and invites us towards him; finally, he just growls, as the rhythm, and the crowd's dancing, spins harder. I leave at 4am, and they may still be going. This Express is picking up speed.