London International Mime Festival, Barbican Theatre, London<br />Jonathan Burrows/Matteo Fargion, Lilian Baylis Theatre, London

Two unusual shows, the first spectacularly messy, the other obsessively neat, highlight different aspects of the avant garde

When the performer Josef Nadj announced – on a visit to the studio of an artist friend in Paris – that the artworks made him want to get inside one of them, he wasn't just talkingfiguratively: he meant it. The notion appealed to the artist, Miquel Barceló, and thus Paso Doble came about: a performance for two men and 10 tons of wet clay.

At the London International Mime Festival, you're at first unaware of the human element. What you see is a piece of wall attached to a segment of floor – pale, blank and shiny under the stage lighting, inanimate. Stare hard at the wall, though, and you notice its surface start to bubble and heave, pustules rising and bursting softly like warming porridge, which slowly petrifies into a kind of relief map. After several minutes, two dour-faced figures wander on in front of the wall, their business suits suggesting they plan to sell time-shares in it.

This gives the ferocity of their subsequent actions a manic, sometimes farcical, edge. Seizing potter's tools the size of garden hoes, they begin hacking great lumps out of the floor, one of them scooping up lozenges to erect a forest of uprights, the other destroying them as fast as he can with a volley of donkey turds.

Then they turn on the wall, punching knuckle- and elbow-shaped indents, bashing it with brickbats and gouging out footholds that enable them to scale the vertical. At the top, they set to, wrenching up the wall's thick clay corners with the urgency of hooligans on top of a bus shelter.

What prevents this being merely a po-faced variant on paintballing or mud pies is the curatorial care devoted to the evolving picture. Rémi Nicolas's lighting caresses what would otherwise be dull mire into sunset-tinged sculpture. At intervals, one of the men turns a fireman's hose on its drying surface, rendering it slippery, grey and sea-like, until it assumes its former russet crust. A composer and sound-designer is credited, but most of the sticky slurps and slaps you hear are generated live, as the pair gradually become blanched and encrusted, their suits beyond redemption, their shoes turned to swollen clods.

A morose humour helps things along. Producing unfired terracotta urns, the pair sit on them until they sag, then upturn a series of freshly thrown pots on their heads, sightlessly modelling them with their hands until they crudely resemble the heads of monstrous pigs, roosters and something like a minotaur. These masks are both sinister and funny, though the comedy wears thin with repetition. When Nadj stumbles and crashes, wedging his bull's head against the wall, Barceló turns the hose on him, welding him into the picture, effacing his human form. Isn't it the Koran that says mankind was formed from earthen clay?

Ultimately the pleasure of Paso Doble is its brevity and circularity. The whole thing is wrapped up in 45 minutes, and there's the 10 tons of clay, all ready to be smoothed over and attacked afresh next day. The show from Jonathan Burrows and Matteo Fargion, currently playing weekends at Sadler's Wells Lilian Baylis studio, could do with a similar dose of compression – which is odd, considering its material is as spare and as sparse as it gets.

In 2002, choreographer Burrows joined up with composer Fargion to create Both Sitting Duet, a silent, chair-bound semaphore of a musical score by the American minimalist Morton Feldman. Its witty execution tickled audiences' fancy, and it became the surprise hit of the international circuit. Its sequel, The Quiet Dance, took that minimalism further, though paradoxically it was also rather noisier. Here, the gnomic pair, identically dressed and identically bald, took the notion of "steps" at their word, presenting a series of flat-footed walks, each executed with an increasing stoop as if descending a flight of stairs, to a vocalised decrescendo (something like the habitual "Aaaaaaaah!" emitted in the dentist's chair).

Two years ago came The Speaking Dance (perversely with mouth-organ and singing), and now, for the first time, all three pieces are performed in one programme. At 180 minutes, including intervals, this strikes me as too much of a good thing, though it's instructive how quickly one adjusts to a severely restricted palette (which is to say, three hours of very little happening – certainly nothing one would normally call dance). Any new tic woven into the regular fabric – whether hand signals or walking steps or verbal nonsense – arrives with the force of a steam train. The repetition itself becomes comic, too, not just because it's doggedly absurd, and performed with a truly wondrous virtuosity, but because we laugh at ourselves for finding "nothing" so absorbing. How minimal can minimal get before it disappears?

"Burrows/Fargion": Lilian Baylis, EC1 (0844 412 4300) 25-26 January