Merce Cunningham Dance Company, Barbican Theatre, London

You can't stop Merce Cunningham performing. Arthritis may, after a long battle, have trapped his 83-year-old dancer's limbs, but his voice remains free. Last year he spoke in John Cage's radio play An Alphabet, staged at the Edinburgh Festival and elsewhere. Now he brings his voice and presence to his 1965 piece How To Pass, Kick, Fall and Run, revived this year as part of his company's 50th anniversary celebrations.

He sits with David Vaughan (writer, performer and company archivist) at a table. White-haired fellow conspirators in jazzy outfits, they read the anecdotes that make up Cage's accompaniment. Sometimes their voices overlap, telling two stories simultaneously. Their delivery is so impeccable, and the content so funny, they threaten to distract from the dance, except when they yield to silence.

Yet the dance is a fascinating contrast with Cunningham's more recent style. It feels relaxed and freewheeling, where today Cunningham prefers highly evolved, controlled structures. It has a palpable warmth, a straightforward, optimistic sense of life that presents the dancers as themselves rather than intergalactic travellers or fantastical wildlife. As the title suggests, the movement is relatively simple and pared down – runs, skips, jumps, mixed with more dancerly sequences.

Robert Swinston, who helped with the revival, opens with a solo. Then two couples mould shapes and slowly collapse backwards, while a duo of women arrives, glued at the hands and trying to tear apart. In the prevailing atmosphere they are more playful than sinister, as is the bobbing trio, where the central man spins round and alternately gives each woman a push, to make her spin as well.

The informality is heightened by the dancers' practice clothing and an absence of decor, leaving stage apparatus exposed, whereas Way Station (2001) and Loose Time (2002) have sophisticated settings. In the former, Charles Long's towering, spindle-legged papier-mâché sculptures create a spidery architecture for the dancers to weave round and under. They might be citizens of a surreal Minoan city or day-trippers in a futuristic theme park. Halting in strange poses on demi-point, they seem frozen for an eternity, figures caught in an antique mosaic. The drawback is Takehisa Kosugi at his console, twiddling the knobs for his score of hiccuping rattles, snuffles and tweetings. The irritating sounds threaten to sabotage the vivid world produced by the convergence of movement and design.

Loose Time has less resonance, more austerity, with its unison couples and massed lines. Terry Winters's mesh backdrop is striking, though, as is Christian Wolff's music; accumulating instruments that ricochet through speakers round the auditorium. Best of all is a woman's solo, her limbs deciding on one direction then abruptly changing for the other. The effect is a concentrated, spiky sequence of surprises, epitomising a lifetime's achievement of surprises that continue today.