NINA SIMONE has never been a comfortable musician to see live. A powerful performer, she is formidably dedicated to her art. It's hardly surprising, then, that the only artist she resembles is Billie Holiday (or that references to Holiday should punctuate her set).

Simone breaks all the rules to emerge with a style that, while its nuances range from Copeland and Gershwin to avant-garde and from African music to Handel, owes a debt to no one tradition, nor to any contemporary.

For some time, culminating in last year's concert appearances here, it seemed that Holiday's personal dilemmas were finding a repeating pattern in Simone. So it was to be expected, then, that Tuesday night's audience, who gave her an ovation simply for walking on stage, tall and majestic in her multi-coloured robes, seemed to be applauding not merely her stature, but the fact that she'd made it there at all.

In the event, there was no repeat of the stumbling, nerve-wracking emotionality of last year. At one point in her set Simone referred to the occasion by calling out to two people in the audience. When they answered, she gave them a public reassurance: "Hey – I'm well again."

From her early days as a public advocate of black power, Nina Simone has been seen as among the strongest political figures in American black music. Dedicated and committed to preserving a heritage, to presenting dignity and strength, to an intractable refusal to mould herself into "commercial" acceptability, Simone remains as far out on a limb as ever.

Even the way she puts together and presents her set expresses a political stance. She performs the numbers she chooses, that reflect her mood, rather than those the audience expects (there were hardly any of her newer songs, and one attempt to deliver the brilliant 'Baltimore' was simply dispensed with in favour of the unexpected Hall and Oates' 'Rich Girl').

She expects her listeners to work, too. Sitting behind her grand piano, or prowling the stage – feet hanging, head back, arms outstretched in a Zulu dance – she commands the audience with an almost intimidating presence.

So we hummed three-part harmony when she needed background for her acappella; provided finger-snapping rhythm when she needed accompaniment; and call-and-response on her gospel numbers. The reward was one of her rare and dazzling smiles, and the occasional tearful, meaningful silence.

Throughout the two-hour set, Simone cajoled and tricked us, and was occasionally breathtaking. She remains impressive not least because, while you may constantly marvel at her dramatic improvisations on Brecht/Weil or Gershwin, she can also take quite insignificant songs (like 'Rich Girl') and completely efface their origins.

Tuesday night started with an ovation and ended with a standing ovation – rare indeed.