Trisha Brown's Slippery Acrobatics. DANCE: REVIEW

YOU never know, when the curtain goes up, what a new Trisha Brown dance will look like. Brown usually incorporates novel extremes of costume, gadgetry, visuals, and acoustics into her stage landscapes, but, more interestingly, each dance represents a further stage in Brown's ongoing experiment with the dance medium itself. ``Astral Convertible,'' which had its American premi`ere during the Brown Company's recent week at City Center, looks like some kind of flight training for a moon launch. The hi-tech environment for the dance, devised by Robert Rauschenberg, consists of eight onstage equipment frames of different heights, with tape recorders and lights placed on them. Nearby, sensing widgets set off the lights or sound sources when a body approaches their scanning field. The lights aren't the usual theatrical kind, but small and brilliant, like car headlights aimed straight into the space, and the tape recorders have different selections - mainly saxophones and electronics in different tonalities - by Richard Landry, which play intermittently and overlap during the dance.

The nine dancers might have been turned loose in this automated laboratory in order to test how they can move in unfamiliar conditions. When you first see them, they're lying on the floor in their silver unitards, gently snaking one body part after another into new positions. They seem to be trying out as many new ways as possible to be in contact with the ground while keeping some parts of their bodies off the ground. Face down, they might slide an arm under the chest and let the crosswise pull rotate the whole torso till the upper back is on the floor and maybe one hip, with a leg reaching in the opposite direction.

For a long time, Trisha Brown has been developing a fluidity in the body that enables the dancer to move any part in any direction and any sequence, as if it were all connected and well-oiled. In ``Astral Convertible'' she makes a point of halting this eccentric flow at almost any point. The dancer simply stops in her or his tracks, creating crooked, twisted, and impossibly off-balance shapes. After a time, the successive motion resumes. These poses, sometimes engineered in unison by several of the dancers, give a sense of visual coherence to the choreography. Something we usually perceive as an ongoing energy flow is momentarily stabilized or caught like a video freeze-frame. THE dance moves into themes of partnering, at first just a series of odd lifts and supports. Lisa Schmidt and Gregory Lara swirl around each other. She springs up in the air or falls suddenly and softly, her trajectory suspended for an impossible instant, and just as you find that he's holding her under one arm or bracing her with his hip, they've whisked apart and into the next thing.

The other dancers join in this display, and you'd think - with all of them careening around and up in the air and butting into each other - it would be dangerous or violent. But it isn't. Somehow it seems they can spread out their energy into all parts of their bodies equally so that they almost levitate. They don't so much rebound from one of these contacts as keep their weight off the supporting point. For instance, a man is corkscrewed on the floor with one flexed foot in the air, and a woman streaks up behind him, steps on his foot, and slides her whole body over it without pausing, the way you'd go over a low fence.

By the end of the dance the whole group is doing these slippery acrobatics, and two or three people even support two or three others at a time in collective throws and catches.

One doesn't often see a dance that progresses choreographically. Hardly anything in ``Astral Convertible'' is repeated, yet it isn't disorienting or overloaded because, just as you're losing track of one set of remarkable movement ideas, they lead you on to another. Brown's dancers - in addition to Schmidt and Lara, they are Lance Gries, Diane Madden, Nicole Juralewicz, Carolyn Lucas, Shelley Senter, Wil Swanson, and David Thomson - look amazingly intelligent, clean, and capable, as if defying the laws of physics were just another day's work to them.