Rosas, Sadler’s Wells, London

Anne Teresa De Keersmaeker’s En Atendant is a dance fading into the dark. The performance of her company Rosas emerge from deep shadows at the back of the stage, and vanish into darkness again. By the end, the last dancer is a dim figure, moving away under failing light.

De Keersmaeker has always demanded patience from her audiences. The Belgian choreographer made her name with dances to Steve Reich, minimalist performances that build tiny changes into repeated sequences. En Atendant is gruelling even by De Keersmaeker’s standards; it runs for more than twenty minutes before we see a step.

Instead, the work opens with a long, strange flute solo by Michael Schmid. He breathes carefully before raising the flute to his lips, then produces an endless wail, a continuous note that uses astonishing breathing techniques to stretch on forever.

En Atendant, which opens a London season of recent work, was created for outdoor performance in Avignon. It was danced in the evenings, under natural light. At Sadler’s Wells, the work is lit by stark bank of fluorescent lights over the front of the stage, lighting the stalls as well as the performance space. There’s a neat line of sand at the front of the stage, soon smudged and kicked by the performers’ feet.

Much of the music is based on the 14th-century style ars subtilior. Soprano Annelies Van Gramberen sings an opening phrase several times, breaking off and starting again. She’s joined by Schmid and string player Thomas Baeté in a touching, melancholy trio. Late on, they push the music into outright discord, musical lines turning deliberately sour.

At last the dancers start moving, huddling into a group and leaning at angles, like an interrupted pileup. They lope across the stage in loose, light steps. The movement is unemphatic, almost weightless, but very precise. Bostjan Antoncic breaks the mood with a flailing, aggressive solo, kicking at the sand and flinging himself angrily across the stage.

When Sue-Yeon Youn tips sideways, another dancer comes to hold her hand, so she can hold the position longer. When two women try the same tilt, one is supported, but the other folds down to the ground. The dancers sketch out steps, then break off. Unexpectedly, the dancers change costumes, women borrowing the men’s trousers. Another man strips off and lies in the dim light. The banks of harsh fluorescent light start to go out, mimicking the effect of twilight.

De Keersmaeker’s dances can be a strange mix of wild and pedantic, tightly patterned but unexpected. You have to wait a long while between such moments. This is not a fast-paced show; sometimes it feels like an endurance test.

Rosas season continues until 9 November. Box office 0844 412 4300.