Cathy Marston, Linbury Studio, London<br></br>Wim Vandekeybus, Sadler's Wells, London

Cathy Marston has a rum job at the Royal Opera House. Appointed as its first associate artist 18 months ago, she has so far been required to pick up the coat-tails of two commissioned operas in the main house and produce a "response" in dance downstairs at the Linbury - a very tall order both times. It was hard to imagine a less dance-suggestive story than that of Sophie's Choice, the Holocaust guilt scenario that underpinned her project of 2003, and it's hard now to think of a more over-fingered narrative than The Tempest. Marston is far too sophisticated an artist to want to tell it straight, and far too canny, at 27, to willingly risk comparison with a string of inspired adapters that leads from Henry Purcell to Derek Jarman and now to Thomas Ades (see opera review, page 10).

So Marston chose diversionary tactics. She devoted half her show to a pair of oblique character studies inspired by Shakespeare's text, one of them involving a character who doesn't appear in the play. For the rest she homed in on the extraordinary orchestral writing of Ades, using an abstract piece he composed some time ago. Links were thus tenuously maintained with the operatic Tempest raging upstairs, with Shakespeare and with Ades, but separately, as if they'd never met. The result - given a scant three performances, too few, surely, for all that effort - was a genuinely illuminating counterpart to the event on the main stage.

As a choreographer who outgrew the "promising" tag some time ago, Marston seems to have learnt an important lesson: that it pays to invest your emotional energy in a single potent image rather than spreading the interest more thinly. Her duet for Gildas Diquero and Martina Langmann, as a mud-smeared Caliban and Sycorax, his hag-witch mother, contains not much more than one brilliant dance idea, and the rest merely resonates in sympathy. The labour howls of Sycorax under a greenish light make an arresting opener, but it's Marston's suggestion of the birth itself - the top half of Diquero's body emerging from somewhere around Langmann's middle - that made me really sit up. This is followed by a joyful, vernix-smeared romp of push-me-pull-you cartwheels, with Caliban's body half-in, half-out of his mother's belly. It's both funny and tragic (she later dies), and beautiful and revolting. And it ushers in that element of sorcery, benign or otherwise, that lies behind everything that happens on Caliban's island.

The second searing image of the evening comes when Jenny Tattersall's Ariel appears to float and dip and hover like a seagull on eddies of breeze around Prospero's head (no strings, it's all down to dance illusion). Jules Maxwell's spare score summons lonely seascapes beautifully, before spoiling its pitch with a crooning rendition of WH Auden's poem The Sea and the Mirror, whose deliberate bathos in this context falls horribly flat.

Choreographers such as Marston, who is led by music and listens to it critically, are often hailed as musical. But to my mind it was musically inept to set so monumental a score as Ades's Asyla, with its Rite of Spring-type climax and great cliff-faces of sonic complexity. It simply swamped the five dancers and everything they did, even the gutsier moments when they bounced off vivid elastic strings strung across the space like boxers' ropes. Better, surely, to choose smaller music, music that can be affordably done live. That's what the Opera House should be about, upstairs and down.

A live rock band played along to Blush, the latest extravaganza from the Belgian crash-dance veteran Wim Vandekeybus, but it was so deep in shadow at the back of the stage that its presence barely registered. This was a shame, since the lyrics of David Eugene Edwards' songs were heaps better than the drivel spouted by the dance company. They harangued, they gibbered, they screamed, they endlessly asked members of the audience about their sex lives. The show seemed initially to be about love and its physical manifestations, but after a while, trying to match what I was seeing with this theme defeated me. A girl comes on holding a live frog by its back leg. Someone else produces a blender and, hey presto, girl gets a glass of livid green frog-shake, which she drinks contentedly. A more disturbing scene shows two men sexually molesting a female corpse. Earlier we have a woman rape a sleeping man. To what end? Surely not simply to make us blush - that would be too puerile. But I'm still struggling to make sense of a cinematic imagination that can shoot ravishing underwater film and have dancers dive head-first into the screen, seeming to re-appear in a burst of foam and dolphins, and then think it clever to send on a woman wielding a live chainsaw. Sensational, certainly. But sensation without discipline or constraint, as every onanist knows deep down, is not in the end very interesting.

jenny.gilbert@independent.co.uk

'Blush': Glasgow Theatre Royal (0141 332 9000), Tue & Wed; Newcastle Playhouse (0191 230 5151), Fri & Sat