Enter: Merce Cunningham: Approaching 75, the American choreographer Merce Cunningham is like a child with a new toy: in this case a computer which allows him to put his company through its paces without breaking sweat. By Judith Mackrell

For the last couple of weeks New York has been paying its respects to Merce Cunnigham who, at nearly 75, has become the iconic Wise Man and Genius of American modern dance. Though his real birthday isn't until April, two major dance events have been anticipating the celebrations. Mikhail Baryshnikov's White Oak season at the State Theater was dedicated to Cunningham, with Baryshnikov dancing in a revival of Cunningham's 1970 classic Signals. And Cunningham's own company is currently appearing in a two-week run at City Center.

A major artist's three-quarter century is the kind of event Americans are good at making a splash about. But for Cunningham, when we spoke a couple of weeks ago, it was business as usual. No fuss, no hype, no glitzy appointments, just getting on with rehearsing the current rep and working on some new dances (he is still producing them at the rate of two or three a year).

The company is housed at the top and bottom of a graffiti-scrawled building in Greenwich Village. The dance studio - on the 11th floor - is vast, light and airy, but the offices on the first floor, where we're due to meet, are cramped. It takes Cunningham several minutes to make the journey down because the lift is old and slow. Cunningham is one of the greatest figures in dance today but his surroundings are hardly grand.

He's reached the age where, bar illness, he always seems to look the same. The elegantly-held head, with its halo of thinning, curly grizzle; the big boxer's nose dramatised by lean cheekbones; the spry body that belies arthritic stiffness - all these are unchanged from when I interviewed him several years ago. His manner is unchanged too. He converses with an old-fashioned graciousness that makes you feel you've all the time in the world (even though his nice PR is itching to give you only 20 minutes). His talk is spattered with the same disorientating leaps of logic. He remains almost comically adept at deflecting personal questions. One tentative reference to the death of John Cage, Cunningham's long-time partner and collaborator, produces an instant, shameless digression into a story about someone completely different.

Unchanged, too, is Cunningham's big, merry laugh. It frequently accompanies talk about his latest passion, which is his unique dancing computer.

Designed at the Simon Frazer University in Vancouver, this toy had allowed Cunningham (in theory at least) to become history's first choreographer to invent movement without the aid of human bodies. Its resources are far larger than any company. Firstly Cunningham can call up a screen peopled by as many figures as he wants, which will move in step to his every command. ('You know,' he chuckles, 'Petipa would have taken to this immediately.') Secondly, he can call up a much larger single figure, and using a cursor instead of the traditional dancing master's stick, nudge it into whatever shape, through whatever steps he chooses. These movements can then be programmed on to one or any of the multiple figures, and there's a third function that inputs the rhythms.

The joy of this computer isn't just that Cunningham can work while his human dancers are resting. It also conjures up movements he's never imagined. 'You often get photographers catching the body doing things you never saw before. With this figure, if you stop it between positions, you see things you didn't know were there.' He says he discovered new ways of using arms ('they've gotten rather exotic,' according to one dancer); and he can build up movement phrases that are even more complex than in his pre-computer days.

That's saying a lot, since Cunningham has always combined movements with an agility and unexpectedness that makes most other choreograhers seem monosyllabic. With the computer as an extra brain the possibilities for invention seem unlimited - though he says the computer can be a bit slow to keep up: 'It's like a mule, it takes time to bring things up, it's kind of tired and it's too full.' Even so, it allows him to make choreography so rich in detail that he can no longer store it in his head. All this, of course, has to be transferred on to the real (and less) tractable bodies of his dancers and the process changes, transmutes and grows in the studio.

Naturally he laughs: 'I have certain parameters; what you can do on computer you can't always do on yourself, like turn your head round several times. I used to worry that the dancers would have trouble remembering it all, but . . .' - he smiles with grateful admiration - 'they are amazing.'

If all this sounds like dance by microchip, the works that have come out of the computer so far have apparently been as mysterious and potent as any Cunningham has made. Enter, whose title pays its respects to the all-important computer key, is one of several that have triumphed recently in America and Europe, (the New York Times referring to its 'Matisse-like design' and its 'profoundly emotional atmosphere').

The latest work-in-progress, Ocean, is also being made with the couputer - which partly explains its terrifyingly ambitious concept and scale. It lasts one and a half hours: 'I figure that's the length of a movie so people won't think they have to leave in the middle,' and it is designed to be performed in the round. The audience sits all round the 15 dancers and around them will be 112 musicians all performing a live score in competition with a tape of underwater sound.

While the musicians time themselves with stopwatches (there'll be no conductor), the dancers have to deal with the fact that there's no 'stage front', so that any phrase of dance can take off in any direction. 'You can see what the possibilities are, there may be seven people doing different things all going in different ways.' And Cunningham has no idea how he's going to cue all the dancers and musicians to start on time. When I ask why he does this to himself he says, with devastating understatement: 'I guess I just like things being complex.'

Cunningham was once a byword for all that was most stubbornly difficult and unballetic in modern dance, yet more and more classical companies are now begging to have his works. He thinks his movement is difficult for ballet dancers, it has 'a complexity and force different from what they are accustoned to'. But it doesn't seem to worry him that they can't perform his choreography exactly as it was made. 'I don't think of them as doing it wrong even if I don't like it. I long ago decided that the choreography I do is one thing, the performance is another, and the reception by the public a third.'

I pick up some pretty clear signals that Cunningham actually distrusts ballet's current flirtation with modern dance. 'I always thought that if you studied ballet that was how you danced.' But typically he won't voice his criticisms direct - they all come out through telling hesitation and through what is, even for Cunningham, agonisingly eccentric syntax: 'I don't see much dance but I know New York City Ballet has had deviations, so to speak, into ideas about contemporary dance.'

Polite and scrupulous as he is, however, Cunningham is clearly relishing the prospect of flexing a little artistic muscle at Baryshnikov, before the latter dances in Signals. He is 'really looking forward to seeing the performance: I'm going to say it's going to be a treat.' But 'Misha and I had our photographs taken together the other day, and he was doing one of the steps from the piece and . . .' - a huge, pleased grin - 'I could see that I had to tell him something about it.'

The Cunningham Company is to appear at the Edinburgh Festival this summer and at Dance Umbrella in London this autumn

(Photograph omitted)