El Gusto, Barbican, London

There's nothing like a story of veteran musicians reuniting after decades apart to sell a world music act to the media – look at the success of the Buena Vista Social Club and Orchestra Baobab. But I wouldn't be so cynical as to suggest that this was what Damon Albarn had in mind when he went to Algeria to record this group of Jewish and Arabic musicians who were separated by the war of independence in the early 1960s.

For one thing, the Albarn-produced album Abdel Hadi Halo & The El Gusto Orchestra of Algiers lacks the sheen one expects from a would-be world music hit. If anything, the ambiance on these recordings is wilfully lo-fi, as if Albarn had just stuck a microphone in front of the orchestra, pressed record, and sat back smiling as the gorgeous music unfurled.

For another, the CD is not the complete picture anyway – it lacks the Jewish contingent because they were too fearful to return to Algeria for the recording.

But tonight that's all put right as some 40 Jewish and Arabic Algerian musicians take to the stage at the Barbican's Ramadan Nights festival. For more than three hours they play their songs of love, lust, loss, and national pride. The thunderous sound is generated by guitarists, oud players, percussionists, and a string section. Add to that accordion, zither, and the pianist Maurice El Medioni, and you've got one hell of a band.

The beguiling music they play is called chaabi (meaning "of the people") and it dates back to the 1920s. There are the ghosts of jazz, chanson, tango, and much more in the mix. But part of what gives the orchestra its distinctive character is that the instruments aren't tuned with the deadening exactitude of, say, a Western classical orchestra.

This creates an out-of-focus effect. But the sheer physical heft of so many musicians with one aim in mind – to bring some of their most treasured national songs to a wider audience – carries everything forward with an intensity that cannot help but hold you transfixed.

Apparently, there are plans for a recording featuring the whole orchestra, so maybe they'll give the Buena Vista Social Club a run for their money after all.

Ramadan Nights ends tonight (020-7638 8891)