Twyla Tharp, Sadler's Wells Theatre, London

A contemporary look at tradition

Twyla Tharp's choreography resembles the way she talks: fast, dense, knowing, designed to impress. At best, the results can be sassy and energising; at worst, it becomes verbose, fixated on its own technical cleverness. Both extremes appear in the programme of mostly recent work brought by Twyla Tharp Dance, once again resuscitated for its present international tour.

There's no doubting the excellence of Tharp's crop of young dancers, the fourth generation moulded to the Tharp style since she began, in 1965. What exactly is the Tharp style? Received wisdom says she invented a hybrid dance. Yet others before her, such as Glen Tetley and Merce Cunningham, fused diverse influences into a new language. What Tharp did was slightly different: she mixed disciplines - jazz, ballet, contemporary and more - without entirely blending them, leaving each ingredient largely intact.

Tharp's choreography, therefore, has a prismatic quality, the eclectic sources flashing before your eyes, the cocktail varying according to the piece. Known by Heart Duet, a classically shaped pas de deux extracted from a fuller work for American Ballet Theatre, has, unsurprisingly, a large dose of traditional ballet steps. Along with the ballet vocabulary are moves inspired by Donald Knaack's Junk Music: percussion that sounds like an attack on saucepans or a second-hand set of African drums. Matthew Dibble's first solo also features steam-locomotive noises, prompting him to lurch into a chugging shuffle. And when Lynd Sing takes over with her solo, she emphasises the score's wooden clacking with chopstick walking on point. This is the best piece of the evening, typical Tharp in its humour, competitiveness and brilliant athleticism. Dibble, formerly of the Royal Ballet, is in his element. He erupts into sudden high classical jumps that seem to float and look all the more spectacular by contrast with the vernacular movement.

The percussive dimension continues with The Fugue, a trio performed by a woman (Whitney Simler) and two men (Jason McDole and Dario Vaccaro) who all look wonderful. They produce their own sound through the patterning of their footbeats on a mic-ed floor, the basic 20-count phrase elaborated through canon, unison and counterpoint. Their floor patterns diverge; the rhythmic cycle accumulates a dazzling complexity, breaks off, cuts back again to basics. Created in 1970 for an all-female cast, The Fugue is a Tharp classic, spoken of with hushed reverence. It would be perfect if it were a third shorter. Tharp's inventiveness operating within such narrow constraints is well-nigh heroic, but the rigorous acade-mic premise eventually palls.

Dance built on that kind of formal principle is a favoured Tharp method, so it comes as a surprise to find that Westerly Round appears to have no real rationale beyond a half-hearted mix of ballet and American folk dance. Emily Coates is full of spirit, but she's the odd girl out, always slightly apart from her three joshing male companions, even when she matches their hyperactive antics. Charlie Neshyba Hodges wins rousing applause with his bravura tricks. But the piece's self-conscious playfulness descends into cuteness and doesn't add up to much.

More substantial is Surfer at the River Styx, set to a dark, swirling score by Knaack again. Characters emerge from the continuum of movement: two sinister pairs of men and women; two other men embarked on a journey full of dangers and obstacles, before arriving at a kind of apotheosis.

Scott Zielinski's lighting creates an underworld of black pools and sinister beams. The whole thing is apparently an exploration of Euripides's Bacchae, which is nice to know but no help at all. The narrative, if that's what it is, is so embedded in the dance, it becomes that impossible phenomenon: an abstract story generalised to the point that it could have any number of meanings.

Well, that's Tharp: she may be a commercial hit, but she still manages to annoy, challenge and compel in equal measure.