FEW EYEBROWS are raised nowadays when a choreographer takes on an opera, particularly opera of the early variety. Purcell, Rameau and co provided generous cues for dance, and modern treatments such as Mark Morris's Dido & Aeneas (with Morris himself as a gorgeous Dido, the singer tucked out of sight in the pit) have gone down in dance, if not in opera, history. But for a dance specialist to tackle the central business of how the singers present themselves on stage - that's a challenge of a different order. And it's one the American Trisha Brown, best known for her free-ranging experiments in post-modern abstract movement, may be uniquely qualified to take up. She's spent much of a 40-year career exploring silence. Brown showed her production of Monteverdi's 1607 Orfeo at the Barbican last week, and proved her imagination to be as free of encumbering convention as opera's first great composer himself.

The director's major coup is to make her own company of nine dancers indistinguishable from the singing chorus, so that the visual flow from musical number to number is unbroken. Performers are constantly spooling off to regroup in bewitching spatial formations, weaving, dodging, or simply walking serenely to form abstract patterns on the stage from which to sing. The soloists, likewise, take a stylised animation which is not quite dance, yet is a long way from conventional stage behaviour. All this allows us to see and hear Monteverdi's masterpiece not as a 400-year- old pageant of nymph-and-shepherdry, but as a trenchant and timeless piece of wisdom - a Venetian tragedy in the Greek mould.

Many of Brown's most dazzling movement ideas are forged in conjunction with Roland Aeschlimann's ravishingly simple designs. The entire piece is played against a large lighted sphere which depicts a gradual solar eclipse - inching from light to dark (for the Underworld scenes) and back to light again, when we see the gold-cocooned body of Apollo rotating like the a hand of a clock around the fiery face of the sun. Earlier, Brown creates a cool aerial ballet for a dancer dressed as a baroque putto, who tumbles and somersaults across the pale blue sphere on flying wires as if buffeted by the soprano's exquisite phrases.

But it's Simon Keenlyside's handsome, honey-voiced Orfeo that most firmly endorses Trisha Brown's revolutionary approach to how singers might make us want to watch as well as listen. His fiendish "Possente spirto" aria, the longest as well as the most technically intricate of any opera written since, is visually empowered by a series of mysterious, t'ai-chi-like gestures and poses which add to, rather than attempt to interpret, the poetic text. In sprightlier mood Keenlyside runs and jostles with the dancers, at one point spectacularly bursting into song mid-leap. And his keening agonies of remorse over losing Euridice a second time are made unbearably poignant by being given sculptural form.

Nothing is imposed on the music: everything springs from it. And in the pit, the Ghent Concerto Vocale under baroque specialist Rene Jacobs produce some of the tautest, most scalp-tingling rhythms I've ever heard from a baroque band. They also manage to caress Monteverdi's strange, elongated phrases into something that at times approaches lyrical ecstasy. This is a production that seduces on every front. Too bad its run was so brief and the Barbican theatre (whose intimacy otherwise suits it perfectly) so small. I believe talks are afoot for Orfeo to return. It can't be too soon.

City commuters at Waterloo and other railway termini in the capital last week were bemused, amused and a few unaccountably enraged by the unannounced arrival of Trainstation, a site-specific project by the Seven Sisters Group. The idea was that five dancers dressed as regular commuters should mingle on the concourse, a dance piece emerging by degrees as the dancers made themselves known by deliberate and repeated movements: a sequence of cheery waves to no one in particular, fastidious rearrangement of their luggage, obsessesive watch-checking. The reaction of an unsuspecting audience was part of the fun.

At Waterloo, however, Eurostar officials decreed that - not wanting to confuse customers any more than they were confused already (yes, really!) - the performance must take place high up behind the huge glass screen which divides the Channel trains from the rest, a fine proscenium, as it turned out. Even without the Candid Camera element, the performance exerted a mesmerising pull on passers-by, who continued to watch intently as, at 19.00 hours, the show was dismantled and the "dancers" emerged in mufti, hallooing this time to real friends in the crowd. This unintentional blurring of boundaries made a nice comment on the nature of performance. Once switched on to receptive mode, yes, we'll watch absolutely anything.

NDT2 is the youth wing of the trio of companies that is Nederlands Dans Theater, and they launched a British tour last week, cashing in on their success here last year. Much has been made of the crackling energy of these dancers - all aged between 17 and 22 - but their opening programme in High Wycombe showed them to be consummate stylists too. In Hans van Manen's testing Grosse Fuge (set to Beethoven) the boys, bare-chested in sweeping black sarong skirts like samurai warriors, stuck a dazzling balance between pantherish grace and clench-fisted machismo, outdoing the girls for glamour.

More entertaining still was Patrick Delcroix's San Reponse, a duet for two boys which mimicked a tribal conflict, using empty plastic water canisters - the sort used to dispense filtered water in canteens - to thwack out rhythms on the floor and hilariously belabour each other. The comic timing was spot-on, the muscular, zany dancing a joy. This time round NDT2 have cracked it: balletic modern dance doesn't come better than this.

NDT2: Blackpool Grand Theatre (01253 290190), Mon; Edinburgh Festival Theatre (0131 529 6000), Thurs-Sat; Woking New Victoria (01483 761144), 16 & 17 Jun.