It's all in the roll of the dice...

Radiohead, Sigur Ros and chance meet in Merce Cunningham's new work, says Karen Wright

Acts of randomness and chance are generally discouraged in the arts. Point at a drip on a canvas and a painter will inevitably talk about controlled incident. However, one artist who positively embraces such things is the 84-year-old dancer and choreographer Merce Cunningham. And his approach was perfectly illustrated recently when his company staged an event to celebrate its 50th anniversary at the Brooklyn Academy of Music (BAM) in New York. The production was a world premiere of Split Sides, a collaborative project bringing together choreography by Cunningham, live music by Radiohead and Sigur Rós, and sets by artists Catherine Yass and Robert Heishman.

Merce Cunningham was born in Washington state and moved to New York in 1939 to join the Martha Graham Dance Company as only its second male dancer. There he met composer John Cage who became the musical director of Cunningham's company when it was founded in 1953. Breaking the tradition that dance had to tell a story, Cunningham choreographed purely physical movement. For him music and backdrops are not meant to support the dance in an integral way but are intended to be quite separate elements. Cage has said: "Merce does his thing and I do my thing, and for your convenience we put it together."

Cage also encouraged Cunningham to introduce chance as a key element in his work and dice soon became a regular feature. My cousin, who knew Cage and Cunningham well, once spent an afternoon with them discussing the serendipity of chance and dice. They broke up their discussion to go to dinner in a local Chinese restaurant. My cousin suggested they order by throwing the dice. Cage and Cunningham were aghast - food was too important!

Before the show at BAM began, I watched Cunningham bring his all-determining dice on to the stage. Mayor Michael Bloomberg was there, as were artists and former Cunningham collaborators Jasper Johns and Robert Rauschenberg, along with Radiohead and Sigur Rós. The roll of the dice would determine five key elements of the performance: what would be danced and when, the order of the backdrops, costumes, lighting and finally the order of the bands. This meant 32 potential combinations. Radiohead won the toss and were told to go first. Both bands retreated to the orchestra pit.

This was the culmination of a year long voyage of discovery for both the bands and Cunningham. He chose to approach the two groups having listened to a stack of CDs, and had expected to work with only one of them. But when they both agreed to take part (on the same day, coincidentally) he decided to use the pair. The only instruction he gave them was to compose 20 minutes of music.

They were not to discuss with each other what they were doing, or consider what the dancers were doing. The first time they would see the dancers would be at a dress rehearsal the night before the performance.

A month ago a question appeared on an official Radiohead web site: "How are your plans coming along for playing that improvised dance event with Sigur Rós and Merce Cunningham? What can we expect?" The response: "aaAAAAAAA HHHHHHHAHHHAHAHAHHA HHH HAHHAHAH aaaaaaaaaaaa aaaaaaaaaaa aaaaaaaa. We are in denial. Fine. Really. Fine. Not telling you what to expect. Not because we don't know because we do. Really we do. Really we do. Thom."

In the event it was clear that Thom Yorke did know what to do as he engaged manically like a cavorting puck dwarfed by a huge mixing deck. The dice had decreed black and white costumes and a back drop by Robert Heishman, a young American photographer whom Cunningham had allegedly met at a party and asked to collaborate. The set was a woodland scene with a large separate moon-like disc creating a sylvan environment. It was a strange juxtaposition with the initially peaceful melodies. But these soon reached a crescendo of jarring jazz riffs created by Yorke and his band on the mixing decks. At one point Yorke was crooning into the mike as if he were willing the dancers to perform. The intensity between him and the dancers was palpable.

Sigur Rós followed with the unveiling of their new musical instrument which had been specially designed for the event: a percussion instrument made from shoes. Sigur Rós bassist Georg Holm told me they've christened the instrument a "bomsett", a word derived from the Icelandic. Their aim was to feel that they were, through their music, "dancing with the dancers". Their performance evolved gradually, using first an instrument composed of their own shoes, then one made out of tap shoes and finally the instrument made out of 12 ballet shoes.

Sigur Rós had visited Cunningham's studio in New York where they'd sampled the sounds of dancers in rehearsal, Cunningham talking and the sound of him tap-dancing in his chair. Mixing these sounds with other riffs onto three CDs, they adhered to the Cunningham tradition of randomness.

For the actual performance they shuffled the CDs blindly. The music started softly with just the sound of hollow drumming and the occasional squeak. Then Sigur Rós began to add subtle layers. A cello bow on a glockenspiel swelled. Holm claims they discovered this ethereal sound "by chance". The dancers performed in front of a beautiful translucent cityscape by Catherine Yass. It was a magical combination.

Split Sides produced a unique set of potential problems. The two groups performing one after the other without a pause meant that there could have been many difficulties with the backdrops, dance and sound. But on the night the two followed each other seamlessly; it even sounded as if the two bands were playing in the same key, another example of pure serendipity, according to Holm. They had decided to use an orgue de barbarie, a music box with the notes punched out of paper rolls, since it reminded them of those music boxes which have miniature ballerinas spinning around inside.

Unlike Radiohead, who seemed to be beseeching the dancers to move with them, and going against Cunningham's rules of randomness, Sigur Rós improvised with their many special instruments while watching the dancers intently. This led to one moment of near comedy where a pair of dancers stretched each other while the band scratched away in the same rhythm. I asked Holm if he felt they were sabotaging Cunningham's intention of keeping all the elements of the performance separate. He said the band felt it was a mini-breakthrough and would love to hear Cunningham's views.

Serendipity is not a word you normally associate with dance or rock music but it permeated Split Sides making it an extraordinarily powerful and rare experience. Cunningham will bring this performance to London next year (whether the two bands will be playing live too has not yet been determined). In the meantime you can see other anniversary events from his company at Tate Modern in London this week.

Merce Cunningham Dance Company: Tate Modern, London SE1 (020 7887 8888) from Tuesday to Saturday