In the Community Room, the George Chelena Chorale is booming "Hava Nagilah" in four parts. Audience members, with blue and yellow buttons that read "Wolf Trap Lives," listen politely.

Meanwhile, in the Studio Theatre, Marie Antoinette is pacing in her prison cell, fanning herself. And in the Theatre, the Richard Cunningham Dancers shimmy and gyrate to a disco version of "Evita" that lasts 18 minutes.

Back in the Community Room, the George Chelena Chorale has come to the finale of its performance--"America the Beautiful"--and the audience applauds loudly, rubbing goose pimples from its arms.

It was a family-oriented labor of love for a popular cause. For 12 hours on Saturday, from 10 a.m. until 10 p.m., the Fairfax County Council of the Arts held an "Entertain-athon" benefit for Wolf Trap at the Reston Community Center. Forty-five local performing arts groups--1,000 dancers, singers, actors, comedians and magicians of all ages--carried on in the Community Center's three arenas, doing what they do best on behalf of Wolf Trap's Filene Center, which was destroyed by fire April 4.

They raised more than $5,500, roughly half of what was hoped for, but then "we may not have been quite realistic" to expect $10,000, said Mia Cunningham, chairman of the Fairfax Arts Council's Advisory Panel. "And I'm not at all disappointed. I think we did remarkably well."

During an art auction, Dottie Schick, chairman of the Fairfax County Democratic Committee, bought the use of a string quartet for $100, a brass quintet for $70 and a group of belly dancers for $60. Asked what she intended to do with the voluptous women, Schick's son, Rory, replied, "She'll bring 'em to the next committee meeting."

The act that may have drawn the most people was political satirist Mark Russell. Russell, with many small children sitting at his feet on the floor, poked good-natured fun at his appearance in a suburban community center, drawing in Reston whenever possible. "This is certainly a high point in my career," he deadpanned. And later, looking around the stark room: "Hmm. Not a bad place for a nightclub."

Among his topics was the nuclear freeze movement, which Russell said will cause people to ask: "How are things at Hiroshima? How are things at Nagasaki?" Pause. "How are things in dear old Reston?" And to the mothers in the crowd, he spoofed a Willie Nelson tune and sang, "Mamas, don't let your babies grow up to be consultants./The neighbors will ask what your child does/and you'll say 'I really don't know.' "

After his performance, Russell said he came to Reston because his schedule permitted him to do only one benefit for Wolf Trap and this was a grass-roots effort. "Also, I needed a liberal audience to break in some new material."

The "Entertain-athon," held in the center behind a suburban shopping center, was indeed a neighborhood effort that began before rebuilding Wolf Trap became trendy. Most participants were Reston residents or came from nearby towns, and said that with the burning of Wolf Trap, they felt as if they'd lost a friend, that going there had been an intrinsic part of their summers. Stillman Carter, a retired machinist from Vienna, said he and his wife, Sally, used to be ushers at Wolf Trap and sold benefit tickets at their church thrift shop. Lisa Clohisy, 23-year-old co-director of the Christina Heimlich Dancers, has been dancing at the International Children's Festival, held at Wolf Trap since it began 12 years ago. "I grew up there," she said.

"It was part of my life, like a friend. My mother and I cried when we heard about it . . . Let me tell you something, when you're on the stage there and dance at the Children's Festival, you look out and see the grass and the wind blows. I can't imagine never having that feeling again."