"EVERY GENERATION has to discover Nina Simone. She is evidence that female genius is real," says Germaine Greer, introducing tonight’s show, one of the highlights of Nick Cave’s Meltdown Festival. "She sings about women’s love — that great, unmanageable, obscene thing."

The woman who plods on-stage 10 minutes later is certainly great, and somewhat unmanageable. Wearing a white, flouncy cacophony of a dress, and guided by two minders, 67-year-old Simone has difficulty walking. She has also become more stocky and wild-eyed than ever. The crowd don’t mind, though, giving her a hero’s welcome.

Simone waits regally for the applause to die down before she takes a lump of chewing gum out of her mouth, sticks it on the side of her grand piano, and launches into a shaky version of 'Black Is The Color'. She is gamely supported by her three backing musicians — musical director and guitarist Al Shackman, percussionist Leopoldo Fleming, and drummer Paul Robinson — but her voice sounds croaky and uncertain. People watch in trepidation, wondering whether this will be an embarrassment or a victory.

Simone can often be a stern performer, but tonight, despite evident health problems, she is in a mellow mood. She announces: "I’m going to sing some songs from my ancestors. Paul Robeson, d’you remember him?", before pelting through a raucous, clumsy version of the gospel standard 'Everytime I Feel The Spirit Moving In My Heart'. Raising her fist in an ANC salute, she conducts the crowd on their clapping spree. With 'Here Comes The Sun', her voice starts to soften, but it’s not until the fourth number, 'Just Say I Love Him', that her rich, mahogany tones really begin to emerge. With a simple ballad about a woman alone yearning for lost love, shades of Simone’s magnificence return.

"This song was one I learned when I was a wee bit of a girl in a holy roller church. Oh Boy, was that somethin’ else. They used to shout so hard," she exclaims, with a change of mood, moving onto the elemental voodoo of 'Sinnerman'. By now she is in her stride, playing the piano with classical flourish, and lapping up the audience’s enthusiasm. At the start of one song, for instance, the crowd begins clapping, then stops. Simone pauses mid-chord. "I’ll take that applause," she says calmly. The crowd, a cross-section of ages and sexes, goes wild. Fired up, she gets up from the piano and paces the stage for the rootsy chant of 'See Line Woman'. "Remember this song?" she shouts, preening, prancing and shaking her ample booty, "Well sing it, goddamnit."

Simone roams across all of popular song, from show tunes of jazz and blues on to dark protest, and tonight she delves deep into the reservoir of musical history and memory. She moves from the restrained anger of the shimmering song-poem images, to the strutting barrelhouse blues of 'Put A Little Sugar In My Bowl', and a plangent, patchy version of 'Porgy'. She then evokes the spirit of civil rights protest with 'Redemption Song', name-checking and blessing Luther King, Mandela and Marley, before giving a driving rendition of 'Mississippi Goddam'.

But the most spine-tingling number of all is 'Four Women', a defiant song about the legacy of slavery. Here we have vintage Simone, staring into the abyss. This is where her genius lies — in her ability to take the listener right through pain, and then transcend it. The stark, lyrical images and the brooding intensity of her voice makes a feted pop/soul newcomer such as Lauryn Hill seem like a mere pretender. There is such supreme conviction, such a definitive quality in the way Simone sings "My skin is black/My hair is woolly", as if hers is the last word.

Simone then astonished everyone by racing through a breathless 'My Baby Just Cares For Me' (she must be in a good mood), and a sorrowful 'Ne Me Quitte Pas', before she exits, diva-style, with a bouquet of flowers and her black-suited minders. Though she doesn’t have the some sleek, poised delivery of earlier days, Simone’s passion and unerring commitment to her artistry remain fully intact.