By Rita Felciano

IS IT POSSIBLE for an avant-garde artist to stay wild into middle age? Isn't the very act of turning expectations upside down a phenomenon of youth? Not if you're William Forsythe, perhaps America's most famous expatriate choreographer, whose Ballett Frankfurt is on its final tour across the country. Last year the 54-year-old Forsythe resigned from his position at the Frankfurt opera house; this fall he'll start up a new company with a dual residency in Frankfurt and Dresden.

It remains to be seen whether Forsythe can make this tale of two cities into a successful adventure, but given what he showed last weekend at Zellerbach Hall (June 3), the prospect seems likely. Maturity hasn't softened his radical ideas about dance, but it has streamlined and sharpened his skill at devising and physically rendering formal concepts. Forsythe stripped dance down to its essence: the human body. Gone were the elaborate sets, shrieking music, and sometimes convoluted ventures into obscure philosophical territory that have characterized some of his past work.

Perhaps the most surprising aspect of the four pieces on this farewell tour was their transparent purity: intent and realization were perfectly matched. This is no small achievement in choreography, where too often ensemble works seem composed of many bat-out-of-hell soloists. It helped that the company features some 30 of the most fearless and athletically trained dancers found anywhere. (Surprisingly, though this is a Germany-based company, not a single dancer is German.)

The opening octet The Room As It Was and the bravura closer One Flat Thing bracketed Duo, for two women, and (N.N.N.N.), a quartet for men. Room was nothing short of brilliant, an extraordinarily detailed series of ever shifting relationships that somehow tied the eight dancers together even though they never appeared as an entire group. The whole piece was like a single pulsing organism. Attacks were sharp, meltdowns soft, the women's pointe work naturally assured, and the top-speed isolations possessed lightning-like power. Ander Zabala made a game out of how close he could come to swinging arms and kicking legs without being knocked out. Jone San Martin repeatedly had her arms manipulated into positions she maintained until she met someone else.

Wearing see-through black tops, Duo's Jill Johnson and Natalie Thomas moved in and out of unisons, creating an effect similar to a conversation interrupted only to be picked up again. Despite this almost tasklike quality, there was something very sensual about the way they filled in each other's negative spaces. Thom Willem's piano score, at first softly pointillistic, eventually became quite melodious and more assertive. Curiously enough, it didn't change the way the dancers related to each other. In contrast, (N.N.N.N.) generated Marx Brothers-style zaniness from entangled dancers. During the opening section, Zabala seemed surprised that he was able turn his arm into a pendulum – he might as well have been Harpo. Most intriguing was that Forsythe built so much of the piece around arm movements.

One Flat Thing's title referred to the metal table (actually, there were 20 of them) that became a platform over, under, and between which dancers slid and ran. The table surfaces and legs – which resembled prison bars – distorted the audience's view of the dancers' lower bodies so they often appeared to be cut off at the waistline. Athletically fierce action sometimes waned to a strange stillness – this was another striking Forsythe piece, possessing widely varied tones.