Martin Creed: Ballet (Work No 1020), Sadler's Wells, London

I wanted to do something with lots of starts," explains Turner Prize-winning artist Martin Creed. "Lots of starting and not much finishing. Except when it does finish." Creed is a disarmingly frank guide to Ballet (Work No 1020), his first experiment in choreography. It's a mix of talk, film, song and movement, making a meandering but cheerful evening.

Creed's new work follows his runners, who sprinted through Tate Britain at regular intervals. Here, he's working with dancers, but restricting himself to the five basic positions of classical ballet. Assisted by rehearsal director Lorena Randi, he uses them to build patterns with dance. Performances are rigorous but relaxed; the dancers giggle at Creed's banter, but all the patterns are clean and sharp.

Creed gets considerable variety from his material. Sometimes the dancers go through a sequence forwards and then in reverse, like a film run backwards. They move from single file to a fanned-out grouping, or end a pattern by lying down. Unison actually brings out the contrasts between the dancers. As they work on the same step, you notice how it changes from person to person.

Highly organised, logical choreography is sometimes called geometric. Creed's dances are like mathematical problems, demonstrating that if x is the case, y will follow. By limiting himself to the five positions, he gives himself a tight framework in which to examine the changing effects of time, speed and direction. These numbers don't flow into dances, any more than musical scales aim at melody.

Between dance numbers, Creed and his band play shouty indie songs with repeated, pessimistic lyrics: "What's the point of it?" or "Pass your bad feelings on". The effect is surprisingly bouncy. Film clips show Creed getting dogs to cross a white space in different directions. The big dog lopes, the little one skitters. "Up and down" shows an erection in profile. To audience laughter, Creed plays an ascending scale as the penis goes up, a descending one as it comes back down.

Throughout, Creed's explanations are genial, bashful without quite being diffident. He'll dither charmingly through a spoken link, until you wonder if the ums and repetitions are set patterns, too.