Eleven boom microphones amplify the sound of two 25-pound blocks of ice melting. The puddled scene is a "sound sculpture."

A herd of cutout cardboard cows are placed over Interstate 280 near the Golden Gate Bridge. They're titled "A New Commuter Image."

Three people in white jumpsuits carry three- by six-foot inflated crosses mounted with audio tapes spouting "Don'ts" from the Bible. They start from the White House, the Capitol and the Lincoln Memorial and walk in the rain for three hours. They're met by blank stares, anti-Klan jeers and an attempt to beat them up.

Some observers are stunned. Others get exactly what they came for:

This is Art.

Back in the '60s, "art happenings" were the rage. Andy Warhol hosted some, Alan Ginsberg starred in others. In the '70s, when Christo wrapped as mountainside in linen ("Running Fence"), when members of the San Francisco Ant Farm drove "The Phantom Dream Car" through a wall of burning television sets, when an "experimental artist" shot himself in the arm, and another covered a Volkswagen with strawberry jam -- they were making "participatory" or "action art," too.

Performance art, as it's now called, is an intellectualized mix of live theater and painting, poetry, dance, film and video. It can be political. It can also be pretentious. It can be the meeting ground of punk rock and art. Dismissing the self-proclaimed "artist" who videotaped the shooting of his dog -- cruel dementia on- or off-camera -- there's some strange new art worth witnessing, not to be found on gallery walls.

An extravaganza of the nonviolent sort will be performed at the Corcoran this Wednesday and Thursday (tickets will be on sale at the door only, at 8 each night). Robert Lango, a prominent New York performance artist, will take over the Beaux Arts-style buildling for two nights of "Empire," a performance trilogy using light, music and movement in a pageant-like show.

Longo's scenario includes a continuous film loop of a man arching backwards (is he dancing or recoiling from a shot?), two slow-motion wrestler/dancers on a revolving platform, a woman singing an aria and additional music by Brian Eno.

Flashing lights will usher the 300 observers each night (at $8 a ticket, $14 for two) to the gallery's upper level for Part Two. There they will confront a continuous film of a Greek sculpture with broken arms between two runways: on one, an elegantly dressed couple will waltz faster and faster until they're boogeying, while on another, sax player Peter Gordon will honk along with increasingly wild improvisations.

For the final filmless reel, 50 extras picked from an open casting call this Sunday night at 7 (at the Corcoran's Georgetown annex, the Jackson School, 31st & R Streets NW), will spin across the floor, lit by 24 pin spotlights so that they appear headless. A "Star Wars" musical finale will top off what the artist calls the "imperial grandeur" of his 45-minute piece. The show's not over, he adds, until the audience walks out the door.

Busby Berkeley 1980s-style? "Not a bad analogy," Longo says. He admits to a desire to make movies and calls "Empire" a cinematic theatrical sculpture." But is it art or entertainment?

"Who cares?" he answers. The distinction doesn't add to the experience.

No use trying to fit it into any philosophical context, either. In the past, artworks were commissioned to celebrate religion, a nation, war. "This kind of art says 'worship," but is doesn't say what," Longo says. "It's about believing in believing.

"When my mother saw the first part performed," he says, "she cried.

Howard Halle, an instructor at the Corcoran who invited Longo to perform, calls "Empire" a "movie in real space. It's happening in real space, but you wouldn't walk into it any more than you would a movie."

As is often the case in performance art, the "point" is subjective. It's evanescent, sometimes comical and generally hard to describe: the classic case of you-had-to-be-there.

But being there doesn't always help. When it's all over, the artists themselves are never sure their audience "gets it." After Steve Seemayer's March 18 "Triple Cross," part of Washington Project for the Arts' "Streetworks" series, Emily Kane, one of the three cross-bearers, said, "People's reactions confused me.

"A lot of joggers just smiled," she recalls, "it didn't faze them. And kids reacted as though I was some kind of clown. One woman said, 'Honey, are you a born-again Christian? I am,' even though the tape was playing an anti-Christ, anti-political, anti-social-conditioning message."

WPA regularly brings in performing artists who forsake paint and canvas for creations in 3-D and real time. Among those appearing locally is Sherman Fleming, an art teacher at Montgomery College with a background in dance and mime who is also one third of a multi-media lecture group called Rod Force (and the Anti-Formalist Reclamation). His performances, which have drawn national notice, are about physically, to wit:

Last year Fleming hung himself upside-down with mirrors on his body to the sound of James Brown music in a piece titled "Cold Sweat" -- a statement of some kind, surely. On Wednesday at WPA, he'll strap himself into the same paratrooper boots to be suspended again, this time dressed in feathers and sweatpants, doing a combination of island initiation rites and dance, rotating in a circle. He'll be accompanied by a jazz musician improvising for the 10 minutes to one hour that the piece may last. "The length will depend on my momentum," Fleming says.

The artist's body is a common ingredient in performance art: Marcel Duchamp used his in 1921, shaving a star shape on the back of his head. At WPA earlier this month, Carolee Schneemann, known as "the woman who uses her body as art," performed "Fresh Blood -- A Dream Morphology." Some 110 people observed her slides, tapes and at times undressed movements, amassing stray thoughts on the themes of sex, female anatomy and male taboos. "There were some stunning moments, but I thought it was a little bit dated," said Kim Kovac, a WPA staffer.

If nudity in performance art alienates some viewers, violence surely puts off others.

"I don't know what to do with the violence, but when you read about it, it becomes a very spiritual thing," says WPAs Melinda Lewis-Matravers, by way of an explanation.

"Each artist is unique and vitally concerned with communication," she says, "except one West Coast artist who put himself in an isolation cell for a whole year."

Do you appreciate that as an artistic achievement?

"Well, when I read about it, a lot of these things work," says Lewis-Matravers.

Pretension runs rampant through much of performance art. One California artist took a job as a waitress in a doughnut shop and titled her performance "Waitress in a Doughnut Shop." When is good service an artistic achievement? Just tip 15 percent and call it art.

Theatrical art pieces are easier to appreciate. Last month at WPA, Eric Bogosian performed "Men Inside," an acting/dancing monologue depicting 12 male personalities, from birdwatcher to disco dancer to junkie. What makes him an "artist" as distinct from an "actor"? Is Andy Kauffman a comic or an artist? It's hard to know what without a scorecard.

Sometimes amusing, sometimes shocking, political or anti-political, performance is among the more radical art forms. Art historians say performance artists' hearts belong to Dada. Also to the Bauhaus, Surrealists and Futurists. In the end, the genre defies category. Some practitioners say that the form is dead, its cutting edge dulled years ago.

Maybe it's not art at all. Or maybe you just have to be there.

ACTS OF ART EXHIBIT A" -- Friday at 8 in the Corcoran's Hammer Auditorium, 17th and New York Avenue. A performance ensemble under the direction of playwright, director and mime J. Garrett Glover, "Exhibit A" will present "9 x 9 PERFORMANCE '81." The revue is free, covers such themes as "The Individual and Society" and "The Human as Tree," and aims to explore the history of performance art. Call 628-9484 for information.; "EMPIRE" -- Wednesday and Thursday at 8 in the Atrium of the Corcoran. A performance trilogy by Robert Longo, "Empire" is a benefit for the Corcoran School of Art. Tickets, available at the door, are $8 each, $14 for two, $6 for Corcorn members. "FAULT" -- Wednesday at 8 at Washington Project for the Arts, 1227 G Street NW. Rod Force and the Anti-Formalist Reclamation Organization presents an "inter-media production." $1 donation.