Cesaria Evora, Royal Festival Hall, London

Lift up your voice

What is it about Cesaria Evora? I've yet to meet anyone who, on first hearing her voice, fails to go down like a nine-pin. Comparisons are often made with Bessie Smith and Billie Holiday, but all she really has in common with those great singers – apart from her African origin – is her incorruptibility. Her unique timbre has nothing to do with Bessie's feisty

horn, or Billie's sophisticated sax.

It's easier to describe what Cesaria's voice doesn't have: no affectation, no implicit invitation to share her tragedy, no self-conscious art. Within its small baritone register, and its level dynamic, it's the cleanest, most unadorned voice on earth.

They were hanging from the rafters to hear her on Friday, and all hell broke loose when she finally made her appearance, clumsily stumbling up the steps – barefoot as usual – and plonking herself in front of the mike with her boss-eyed, earth- mother grin. And what did she start with? "Sodade", of course, and by the time she'd reached the first refrain, half the hall was joining in. This was the song that first launched her to unexpected stardom in 1992, and it's the quintessence of what keeps her there, with its oceanically bitter-sweet reflection of that Portuguese word for nostalgia.

This being record-plugging time, the stage was filled with backing musicians better known as part of the Buena Vista circus. Her new CD Sao Vicente di Longe represents her first shot at fusion with Cuba, and the Cuban players who have now joined her were out in force: three string players, three extra guitars, plus added wind and percussion – a big jump from the simple foursome with whom she originally started out.

Running briskly through a medley of new numbers and old favourites, she was clearly energised by this collaboration, but there's no question about what she most enjoyed. Cape Verdean "morna" ballads – the Lusophone answer to the American blues – go at a languid pace, and depend for their effect on piano, muted percussion, and the dark plangency of the 12-stringed Portuguese guitar. After the obligatory break, she went back to her roots, with lazy vocal swoops, and a monumental underlying calm.

Her warm-up had been the Malagasy group Tarika, and though their act was too neat and slick, it did whet one's curiosity for their CD Soul Makassar, which charts their search for their own roots in Indonesia. And for all the glory of her presence, Cesaria too is best appreciated on disc. But not her latest: Miss Perfumado and Cabo Verde are the ones to go for.