It was 1966. Lincoln Center was sittzng empty. Dark. For the entire summer. Bill Lockwood thought, "What a waste."

He also thought that just because the New York Philharmonic was on summer vacation and the opera seasons were finished, the huge musical and theater facility didn't have to close down. People like to be entertained all the time, not just in the winter. Right?

So he proposed a summer festival. Perhaps devoted to one composer. "No one had done that before," he says now. "There was Tanglewood and the Hollywood Bowl," but those featured works of many different composers. Once the theme was decided upon, a particular composer had to be chosen.

"It seemed obvious that it should be Mozart," he says. "He wrote 800 pieces of music, in every shape and variety -- operas, choral works, chamber and full orchestra. Something for everyone. There was enough variety that you could play a different piece every night and never repeat yourself."

An orchestra was formed, composed of players from the Philharmonic, the Metropolitan Opera, the New York City Opera and even some freelancers. For the first five years, they played strictly Mozart under the name "Lincoln Center's Midsummer Serenade."

Then, in 1970, works by other composers who were directly influenced by Mozart were added to the program. And the festival name was changed to Mostly Mozart.

The Mostly Mozart series has since grown into a seven-week festival at Lincoln Center featuring some of the world's greatest musicians as soloists, with a one-week preview each June at "our sister hall," the Kennedy Center. This week is the 10th anniversary of Mostly Mozart in Washington, and to celebrate it the festival is featuring as soloists flutist Jean-Pierre Rampal, violinist Gil Shaham and pianists Misha Dichter and Shura Cherkassky.

The Mostly Mozart festival is Wednesday through Saturday nights, with pre-concert recitals at 7:30 and concerts at 8:30 in the Kennedy Center Concert Hall. Tickets are $17.50 ($28.50 including picnic supper). There will be dancing afterward on the River Terrace. For tickets and information, call 467-4600.