The world according to Tharp

The Royal Ballet has a new ballet. A whole evening's worth of new ballet. And it will premiere on Saturday night. Praise be to Saint Twyla.

Twyla Tharp - stentorian, granite-haired, Nike-sporting American choreographer - may not seem very saintly, but she has all the qualities required to save the Royal Ballet from perdition. She talks straight, she gets things done, she strongly admires the company, and if her name does not quite trip off the tongue of younger British balletgoers, it soon will. She has chosen to use a popular 19th-century composer (Rossini). The word most commonly used to describe her past work is "optimistic". Praise be indeed.

The company could not afford another non-event. Last November, if you remember, the ever-unpredictable Michael Clark crashed his deadline in spectacular fashion, producing only seven minutes worth of a full-length ballet. In the spring, the celebrated William Forsythe pulled out at the 11th hour, saying he couldn't work with the RB dancers (not collaborative enough, he said). Company morale was never lower. But the Royal Opera House has continued its commissioning roulette, and with the aplomb only a grand old-money establishment can muster, appears to have upped the ante. No one is saying how much the Twyla Tharp ballet is costing, but certainly in terms of stage machinery, costumes, wigs, music, the works, this game is big.

Since arriving from New York in mid-September to begin work with the company, Tharp has managed to remain impervious to the in-house tensions. ("All you can do is the best you can do, and I'd be doing that anyway.") But she conspicuously arrived with Acts I and II already complete and notated, and got them up in just three weeks. The final act has been created on the dancers in situ, notwithstanding constant interruptions from the dancers' other commitments - performances of Swan Lake, Manon and the mixed bill - about which Tharp does not conceal her irritation.

If she came trailing a reputation as a fire-breathing dragon, the dancers seem to be enjoying the heat. This woman knows exactly what she wants, which means little or no collaboration ("though their bodies do suggest things") she apparently asks for neither the ungainly nor the impossible ("You can only do what the dancer can do"); and she does her cast the credit of admiring "their versatility, their bravery, and their good manners". She had not worked with a British company before, and though she made several advance trips to watch the Royal Ballet in class, was surprised to find them "more interesting" than she had been counting on. She says they have inspired her to the limits of her talent.

In rehearsal, Tharp sprawls over the back of a chair and glowers over half-moon spectacles. She barks instructions in a strident tenor or motions to her chic assistant of 20 years, Shelley Washington, to sort out a technical problem. Terms of reference are classical - lots of grands jetes and arabesques en attitude - which must be reassuring to the dancers, though the result Tharp has in mind is more what you might call classical with kinks, a quirky blend of ballet and jazz dance, often executed at astonishing speed.

Critics of her oeuvre - which includes work for her own company which ran from 1965 to 1987, plus commissions for the Joffrey Ballet, New York City ballet, American Ballet Theatre and Paris Opera Ballet - have suggested that the ballet and modern elements seem to be at war with each other. Tharp snorts at this. "I'm not bothered with definitions. I've done some pieces with no ballet technique in them at all. For me it's a case of taking the components that make sense to me physically. I don't label them as this kind of dance, or that kind of dance." She admits that working withRossini's music has made a difference to the movement she creates. "There's nothing like a hummable line for dancing, and this is all so hummable. It makes the body happy to dance, and it's just so buoyant and cushioning for big movement. You get a free ride out of it."

Rossini provides not just the score, but the ballet's theme, which is loosely biographical though not narrative. The title (a last-minute decision) is Mr Worldly Wise, also the name of the chief solo part, danced by Irek Mukhamedov. Tetsuo Kumakawa and Darcey Bussell also have key roles: he is Master Brain-in-the-Bag, she Mistress Truth-on-Toe. Odd, and a bit of a mouthful. Tharp will give little away but gives wry assent at the mention of Pilgrim's Progress. Her ballet is in fact a loose allegory of Rossini's own life, with added roles for quartet, septet, and corps de ballet.

Wasn't Rossini considered something of a low-grade populist by contemporaries such as Berlioz (who accused him of "melodic cynicism")? Tharp has clearly thought about this. "Like Mozart, Rossini had this melodic gift. He couldn't not write a melody, which is both a gift and a handicap. He didn't consider himself an avant-garde artiste and I believe he didn't think that that was a virtue either. He thought there was good music and there was bad music."

We can perhaps infer from this something of Tharp's own attitude to avant- gardery, and to the pleasure principle in dance. "I think there's good dancing and bad dancing. We're all of us interested in doing something we've never quite done before, and there's not a lot of interest in duplicating what others have done. But the notion of doing something impossibly new usually turns out to be an illusion."

Tharp's determination to take full creative responsibility extends even to the score. She herself put together the three half-hour acts of continuous music, choosing and ordering the pieces. Almost certainly the conductor wishes he had got there first. It may not matter to the audience that the famous "Cats' Duet", in F major, segues into a late song, "La Foie", in G, but it's likely to set some teeth on edge in the pit. The selection itself is unorthodox, even a little bit kooky: three opera overtures back- to-back in Act I, then the orchestra twiddles its thumbs: a 12-voice chorus opens and closes the ballet with the stunning Kyrie from the Petite Messe solonnelle, but the rest is late salon songs and piano pieces, what Rossini called his "pechees de viellesse", his sins of old age.

Perhaps Saint Twyla is not so worldly wise herself: perhaps she is indeed a visionary. She is certainly a fervent believer in "the power of theatre, in the physicality of dancers to give the audience a dose of optimism, of joy." She likes the idea of the dedication Rossini put on the title page of his Petite Messe. "Dear God, please accept the following offering of a buffo for admission to paradise." Cheeky, and also self-deprecating. If Tharp had thought of it first, she might have done the same.

n Royal Opera House, London, WC1 (Booking: 0171-304 4000) 9, 15, 18 & 20 Dec, 3 & 4 Jan