Alphabet, Royal Lyceum, Edinburgh

The publicity for this Edinburgh Festival production did not mention that among the cast would be the Right Honourable the Lord Provost of the City, on stage throughout and with one speech as Oppian, a second-century Greek poet who wrote a didactic poem on fishing, called Halieutica. Nor that other locally recruited actors would include the director of the Scottish National Gallery of Modern Art, the director of group community relations at the Bank of Scotland and the director of the Edinburgh Festival Fringe. They supplemented the touring core group and were joined by the voice of the painter Jasper Johns, making his theatrical debut (on tape) as the female alter ego of his fellow artist Marcel Duchamp.

So what on earth, you may ask, is it all about? Well, I've seen the show and I'm still asking the same question. It began life in 1982 as a play commissioned by the West German Radio in Frankfurt from the avant-garde composer, writer and avid mycologist John Cage. He called it James Joyce, Marcel Duchamp, Erik Satie: An Alphabet but said in the text that it was not an alphabet; rather a fantasy. Personally, I would classify it as a joke by the erudite and witty Cage.

What happens is that 13 persons on stage and two more on tape present a collage of statements and thoughts about an apparently arbitrary collection of more or less famous persons, among them Thoreau, Mao Tse-tung aged nine and one of Cage's artist friends, Robert Rauschenberg. The star, white-haired and affably smiling, is Merce Cunningham, choreographer and Cage's long-time partner, making his return to the literary stage after a hiatus of more than 60 years.

He plays Satie, and among the many gems he has to reveal is that he has made an appointment for Freud to analyse his shoelaces (Cunningham, the one-time barefoot dancer, is the only person on stage wearing shoes). There is also the wonderful claim that four or five applications of Satie's third Gymnopédie cured a polyp on a listener's nose.

Other characters include Brigham Young, relating the story that the Mormon church wanted to commission from Duchamp a new version of one of his most famous pictures, but with "many brides and fewer bachelors". A narrator trots busily around the stage, wiggling his eyebrows with coy enthusiasm, while the other performers remain seated on steeply tiered shelves.

Often the text is spoken by more than one person simultaneously, sometimes adding emphasis, but more often decreasing intelligibility. I wondered whether it might be more rewarding just to stay at home and read through the script, but that would have meant missing an occasion that, though puzzlingly eccentric, was certainly bold, unique and, to say the least, astonishing.