The rockapella trio Betty was there, singing in the stately grand foyer with quirky voices, prancing in their decidedly kicky get-ups and chattering in a nonstop, rock-bop yammer. So was Sweet Honey in the Rock, standing in the Concert Hall in sunburst robes, singing to an audience mesmerized in its red-plushed seats. More than 100 local performing artists joined them at the third annual open house yesterday at the Kennedy Center to claim the nationally renowned theater as their own.

"The whole place is yours," announced Kennedy Center Chairman Roger Stevens in the opening speech. And the guests, looking like children overrunning grandmother's house, wandered about with free posters clutched in their fists, with free hats capping their heads and with eyes as big as the Hall of States.

"It's neat," said 10-year-old Tony Muller, "there's something to do everywhere you look."

A clown in fuchsia curls made puppies from string-bean balloons, a nine-foot Uncle Sam swayed by, tantalizing tots and a menagerie of life-sized animals walked around shaking hands and dancing with both children and adults.

The open house, sponsored by the Friends of the Kennedy Center, is paid for entirely from donations from the 30,000 Friends nationwide. And almost 300 volunteers showed up to help escort lost guests, hop around in bunny costumes and man booths.

"People think of the Kennedy Center as only a place for ballet and opera, or a theater for only high culture," said Janet Jones, a volunteer. "Today, it's everybody's culture theater."

Pat Petteway, vocalist and keyboardist with Grazz Matazz, a bluegrass group, agreed. "To play at the Kennedy Center is everybody's dream. Today is great because this gives us a chance to play for people who wouldn't see us otherwise."

The Original Trinidad Steel Band started the day with a sunny, tropical beat. According to the National Park Service, more than 60,000 people sauntered by for the festivities, many in newly unpacked sweaters to protect them from breezy, if sunny, weather that hovered around 50 degrees.

"Washington is a changing community," said Thomas Mader, executive director of the Friends of the Kennedy Center. "People should feel welcome here, because it is not only a political scene, but an art scene, too. We have great musicians here. You don't have to go to New York."

Carol Schwartz came to present to the Kennedy Center a proclamation by the D.C. Council recognizing yesterday as an outstanding day. "After all," she added, "the price is right."

Pat Sheehy, chairwoman of the D.C. Commission on Arts and Humanities who came to the festival to represent Mayor Marion Barry, told the crowd, "The mayor thinks the arts are the soul of the city."

"People are finding that Washington is a home where they are supported as artists," she said. "The next step is to develop an awareness in the audience that {such artists} are out there."

Inside, all three members of Betty told the crowd, "We're getting calls from Finland to Wisconsin, but don't worry, we're still your home-town girls."

And outside on the smooth white pavement of the Kennedy Center, dancing to the beat of Jah Honey and the Unconquered People, swayed a mass of happy reggae revelers.