His greatest moment in the sun

Merce Cunningham's latest Event is being staged beneath Olafur Eliasson's giant installation in Tate Modern

This year's Dance Umbrella festival ends with a double celebration. A week of anniversary Events at Tate Modern marks 25 years of Umbrella and 50 years of the Merce Cunningham Dance Company.

Now 84, Cunningham is a hero of modern dance, one of the 20th century's great choreographers. His dances are endlessly inventive, still testing new possibilities. His most famous innovation, made with the composer John Cage, was the separation of dance, music and design. All three elements would come together at the first performance, independent and equal.

Anyone who loves dancing to music might prickle at this, but wait until you've seen it. Cunningham's sense of rhythm is dazzling, his steps sculpturally lovely. The effect of the different elements is unpredictable. They can tug, distractingly, in opposite directions. They also make extraordinary, unpredictable harmonies.

At Tate Modern, the company will be dancing Event performances - dances reshaped for unconventional spaces. Extracts from past dances, sometimes with new linking passages, are arranged for the space, performed with different music and costumes.

The first Event was performed in a Viennese museum in 1964. The company went on to dance Events in art galleries, in gymnasiums, in New York's Grand Central Station. At Tate Modern, they'll be dancing in the Turbine Hall, under Olafur Eliasson's installation of a giant hazy sun. Cunningham hadn't seen the installation when we spoke last month; he could only guess that it "must be large, to occupy that space". He's especially pleased with the placing of the musicians on the bridge across the hall, "where they will be visible to everyone".

He's decided on three performance spaces, with dancers moving from one to another in the course of the performance. How will they manage it, when the audience is also encouraged to move around? At one Event, held in the Piazza San Marco in Venice, he gave the dancers brooms to clear spectators out of the way. This time, Tate Modern has promised a clear passage between the dance spaces - though Cunningham doesn't yet know how that will work out.

How can he work out performances without full knowledge of the space? The company rehearse as much as they can in their New York studio, which is, he points out, "somewhat smaller" than the Turbine Hall. He worked out that the longest distance between performance spaces should be 150 feet. "The studio is 50 feet, so I asked the dancers to run from one end to the other. They were very helpful." Fifty feet took five seconds, so he's allowed 15 seconds for transitions in Tate Modern, though he expects it will all need adjusting when they get there. He's a practical man: he says the theatre demands it.

Cunningham goes on trying new things. He was quick to make use of cameras, video and computers in his choreography. He's just premiered Split Sides, a dance with music from the rock bands Radiohead and Sigur Ros, which is due to open next year's Dance Umbrella. When his company manager suggested the two bands, Cunningham hadn't listened to Radiohead and had never heard of Sigur Ros. That didn't daunt him. "If you say no," he explains, "that completely cuts off possibilities."

Merce Cunningham Dance Company Anniversary Events: 4-8 November, Tate Modern (020-7887 8888)