The Bride and the Bachelors, Barbican, review And so, the upstairs galleries become the light-filled realm of the "bride," who in this show is identified with Duchamp, while the lower level becomes the shadowy domain of the four eternally frustrated bachelors - Cage, Cunningham, Johns and Rauschenberg - who long to possess her. We begin downstairs with a selection of some of Duchamp's most celebrated works, including a copy of the Large Glass, Fountain (the readymade urinal), Nude Descending the Staircase and the Green Box (the facsimiles of notes and drawings from which he worked while creating the Large Glass). Surrounding these infinitely rich works are paintings and stage sets by Johns and Rauschenberg that are either directly inspired by, or pay direct homage to, Duchamp. As piano pieces by Cage float up from instruments mechanically altered by the composer to sound as little as possible like music, we come to the show's coup de théâtre, a platform on which dance pieces choreographed by Cunningham will be performed on Thursday nights and weekends for the run of the exhibition. Above the stage, Jasper Johns's set for Cunningham's dance piece Walkaround Time hangs suspended in space. Made up of five transparent plastic rectangles painted with motifs copied from the Large Glass, its shifting shadows cast ghostly distortions of the bride and her bachelors down over the bodies of lithe young men and women moving to Cage's music and Cunningham's steps below. When the dancers aren't there, we will hear recordings of the pitter-patter and thump-thump of their bare feet on the wooden floor. Born in France in 1887, Duchamp came to America in 1913. But it is only in the 1950s that younger artists began to take him seriously, and then his ideas were like stones thrown into the placid lake of American art - rippling from one artist and one medium to another. For example, Cunningham collaborated first with Rauschenberg and then with Johns, who both created stage sets for his dancers to move through and around to "music" that might have included police sirens or radio broadcasts chosen at random. Then, in one of the show's many fugue-like moments, Johns turns that choreography back into paintings in a series called Dancers on a Plane, in which dancers" footsteps performing Cunningham's choreography form an abstract pattern of multicoloured hatched lines on a canvas that can only be understood by imagining that we are looking down on a dance floor from above. If the real dancers happen to be performing downstairs, just look down and you'll see how accurately Johns visualised their intricate movements. The most important single idea to come out of Duchamp's work is the concept of the ready-made. By taking carefully chosen articles from everyday life and exhibiting them as art, he demonstrated that something can change its meaning without changing its form, and that what we see depends on what we look for. In the ready-mades, the artist only performs one part of the creative act - each viewer completes the process and completes it differently. And so a man will look at a urinal entitled Fountain differently from a woman because it will instantly occur to him that to use it he would become the fountain, not the porcelain bowl. The idea of the ready-made permeates the work of all the artists in the show. Johns cast two ale cans in bronze in part to explore Duchamp's idea that two things (a real can and one cast in metal) may look exactly the same, but are seen as utterly different. When Johns drew a target above an actual paint brush and blocks of watercolour, he literally offered the reader a chance to finish what the artist began. The more time you spend in this show the more you realise how impossible it is to imagine the careers of Rauschenberg and Johns without Duchamp's philosophy of aesthetics hovering in the background. Duchamp introduced elements of chance and accident in his work in order to keep his own subjective feelings or preferences out of his work. To create the Large Glass, for example, he invented a new unit of measurement he called a "standard stoppage," which he determined by dropping a three metre-long length of thread from a ladder, then measuring the curved shape it made. Rauschenberg, in turn, created his series of lithographs Veils by dropping lengths of fabric on to light-sensitive photo emulsion, while Cage would ask the Chinese book of wisdom - the I Ching - for guidance in writing his musical compositions and Cunningham sometimes did the same with his choreography. Just as you can't look at a work by Duchamp in the same way as you do the work of artists who came before him, so you have to spend time in front of virtually every piece in the show asking why it looks the way it does, how it was made and what the artist was thinking when he made it. It is hard to put your finger on the qualities all have taken from Duchamp in part because they are often so subtle that you sense rather than see them. But then that's true of a lot of the best things in life. What did Duchamp do? He made art more intelligent, more interesting, and a lot more fun. Until June 9