Hasna, Queen Elizabeth Hall, London

World music isn't just music these days - it's a whole way of life, as witness the scene before the concert by the gnawa singer Hasna, who hails from the Algerian desert. The whole place had a Maghreb feel, with the Algerian Women's Association selling raffle tickets to support earthquake victims, while "the best couscous house in town" tempted us in with almonds. Tickets for the show seemed like an afterthought.

Hasna el Becharia took the stage - surrounded by young male drummers - like a cool matriarch. One of them handed her a Spanish guitar, but the sound she drew from it was that of the oud, a bare and angular melodic line. Then she opened her mouth: a smooth baritonal timbre, to match the baritone timbres all round. Then she went up an octave: now her sound was Middle Eastern mezzo, breathy and rough but with a touch of melismatic ornamentation. The style was call-and-response: simple and repetitive, but with a strong forward momentum.

Putting aside the guitar, she was then handed a gimbri. With three strings going over a shape like a shoebox, this is one of the most basic variants in the lute family, but her way of playing makes it sound like a set of tuned drums. She plucked and sang, her young men drummed and clapped, and the Maghrebi women in the audience ululated in return. Weddings and festivities were where Hasna developed her style, and such was the atmosphere she generated here. A simple form of art, not best appreciated in the South Bank's crude amplification, but more engaging on her CD.

This being a hot night, and Omara Portuondo singing up the road at Kenwood, I jumped in a taxi before the end and made my way to Cuba. Earlier in the day I'd listened to the definitive Portuondo CD, La Coleccion Cubana, and been entranced by her lazy grace as she sang a collection of classics including "Besame Mucho". This septuagenarian began as a dancer in Havana's top nightclub, and still performs there 50 years later. After working as a backing singer to Nat King Cole, she had a swift rise to stardom, but, like the other members of Buena Vista Social Club, she'd thought her career was over until Ry Cooder scooped her out of obscurity.

I got to Kenwood as Portuondo was launching into "Besame Mucho". I wished I hadn't listened to that CD: her timbre is no longer feline, and her intonation is approximate. But she still commands the stage, and her Buena Vista chums played up magnificently.

Kenwood concerts do weird things with amplification: the further you go from the stage, the louder the music - and the stronger the argument for not buying a ticket and settling in a field beyond the enclosure. But the huge audience drank moderately, chatted quietly, jigged decorously and - in many cases - took their rubbish home. World music has a curiously civilising effect.