Trisha Brown swoops on stage as the Isadora Duncan of the '80s

Alone on a dark stage in a flowing gray jump suit, Trisha Brown looked like Isadora Duncan doing a juggling act. She wove together a series of fluid gestures that looked both feathery and powerful while giving a lecture on what she was doing with the skill of a seasoned vaudevillian. She started out by announcing, in brief phrases, that talking while dancing was like opening a front-loading washing machine that was doing a load of -- there was a pause as she turned aside and fluidly swooped open an imaginary washer, then finished her sentence -- ``typewriters.'' She went on to describe dancing on the beach, how sh e had to keep moving so as not to drill herself into the sand, and how a ranger came along and ``there was nothing he could do'' -- pause for a really full, stretchy dive sideways with a hand flagging to the side -- ``to get his horse to pass me.''

She was doing a combination of dances, listed in the program as ``Accumulation (1971) with Talking (1973) plus Watermotor (1977).'' It was a kind of capsule retrospective, a good beginning for last week's run at City Center. She started performing 25 years ago in borrowed space in Greenwich Village's Judson Church, but the glossy, tuxedoed crowd that showed up for her opening has recently become more the norm for this dance innovator who survived the '70s by performing in France and Scandinavia. Since h er sold-out 1983 season at the Brooklyn Academy of Music's ``Next Wave'' series, her American audience has grown in numbers and enthusiasm.

Miss Brown's athleticism and a certain lightness and grace, combined with the sense that this dancer had been on a long voyage of discovery, were reminiscent of what we know of Isadora Duncan. Like Duncan, Trisha Brown started out on the West Coast, in Aberdeen, Wash. Duncan had to invent modern dance. Brown learned dance composition at Mills College in Oakland, Calif., before coming to New York to study with Merce Cunningham.

Brown resembles Duncan in her urge to free up movement. ``I wish to be three-dimensional and democratic about my upside-downness and my right-side-upness,'' she said in an interview. ``It's like, the leg can go up and the head can go down. There's an innocence about it. If I really think about it, I run into trouble. But you just toss it up there, and someone comes running by and supports it a minute, or not. . . .''

In ``Lateral Pass,'' her newest work, a woman leaps backward and is grabbed by a man running forward and tossed brusquely offstage. She looks weightless. Of course, male dancers have been helping female dancers look weightless for centuries. But here it's done without heroics. He looks as if he just happened to be going by with something else on his mind. When she comes in for a landing, he just passes her back into the air and goes on along his way.

The effort is concealed, as if Brown were saying, ``Look, over there!'' and you watch the flying dancer. Sometimes a leaper is caught. The catcher doesn't set the leaper down, but holds him or her up there, so it's as if they got stuck in the air. One dancer was lifted off the floor with a rope and dangled over the proceedings before disappearing.

``Lateral Pass'' is a feast of color -- iridescent sets and costumes hung with squiggles of bent metal tubing and flashes of brilliant plastic designed by Nancy Graves. It goes in every direction at once, with dancers pushing off as often from the seat as from the feet and spiraling as often as going straight. The movement is as silky as in ``Accumulation with Talking plus Watermotor,'' but a new angularity gives it punch. And the company is in shape to pack that punch. Stephen Petronio stood out in a b rilliant, squirming trio at the climax of the dance. His back was articulate as he flicked and rolled hips and shoulders, and his head and arms carried the impulses to their illogical extensions. He moves so cleanly that you can see how the seemingly disparate impulses that course through the body in Brown's work are all solidly linked. He and Diane Madden make the moves look eminently sensible.

This choreography is thrilling because it manages to be both flighty and solidly based. Right-side up or down, it has integrity. The Trisha Brown Company appears at the Festival of New Dance in Montreal Sept. 24 and 25, and in November it will be the first modern-dance troupe to appear in Peking since the revolution.