Dancing becomes a little bit complicated on the West Lawn of the Capitol when the number of prospective dancers gets up around a quarter-million, but a lot of people managed it last night during the National Symphony Orchestra's 10th annual July Fourth concert.

Hundreds did it during the orchestra's performance of "La Bamba" and the "Pink Panther" and "Peter Gunn" themes under the direction of Henry Mancini. A few even did it to Tchaikovsky's "1812" Overture, conducted by Mstislav Rostropovich.

Attendance at the Capitol concerts is a much more strenuous activity than taking a seat and hearing music at the Kennedy Center. Never in the history of the Kennedy Center has a concert been preceded by loudspeakers booming out advice on where to pick up lost children or an amplified appeal to "please keep pets on a leash and try to keep them quiet."

The scene was cluttered with blankets, balloons, picnic lunches, fast food stands with endless waiting lines, and lots of forbidden beer cans and wine bottles. Hundreds of people waded in the Reflecting Pool during the concert and the fireworks display afterward. The audience was invited to be active and happily complied -- not only dancing and singing along with some numbers but jumping up to applaud or just work off the energies generated by a clear, warm but not too warm summer evening. A lot of children got up and conducted, some waving their arms, some using small flags like batons and some just making batons of their whole bodies.

When she sang "America the Beautiful," Maureen McGovern invited those in the audience to sing along in the second chorus, and they did -- lustily -- rising and standing through the music as though it were the national anthem, which perhaps it should be.

A half-hour later, singing "God Bless America," Simon Estes invited the audience to sing along, and again 250,000 people (the Park Police's estimate of attendance) rose as though it were the national anthem ... which, perhaps, it should be.

Those who watched the concert live, nationwide on PBS, had a more restful time. They also got occasional glimpses of Beverly Sills. She was invisible to the live audience, but came on the screen several times to act as hostess and to fill the dead time while the stagehands moved things around. On television, the Capitol sometimes looked more impressive than it did on the scene, a bit darker in color and more effectively contrasted with the sky in the background.

PBS viewers also got their fireworks display about 10 minutes before the live audience -- as always, during the final credits of the telecast. This concert must end with fireworks; not to do so might invite revolution. But, as PBS announced, it was unable to show live fireworks, which were delayed for reasons that were not immediately explained. Usually, the fireworks begin midway through Sousa's "The Stars and Stripes Forever," which is always the last number played, but this time the NSO went through a whole Sousa medley with no sign of fireworks down by the Washington Monument.

Fortunately for PBS, videotapes of last year's fireworks were handy to be superimposed on the credits while the live audience waited more or less patiently in the dark. The display (billed as "the largest fireworks display ever designed for the Mall") was worth the wait and was followed by a traffic jam, vehicular and pedestrian, of epic proportions.

Musically, the concert touched all bases from "Blue Suede Shoes," "Peggy Sue" and "Climb Ev'ry Mountain" to "Ol' Man River," the last movement of Dvorak's "New World" Symphony and the "1812" Overture, which Rostropovich conducted a bit more vividly than in last week's performance at Wolf Trap.

On television, the "New World" (music written by a Czech while he was living in the United States) was accompanied by a quick visual survey of events in Eastern Europe since the Iron Curtain was installed: the 1956 invasion of Hungary; the Berlin Wall going up in 1961; the "Prague Spring" of 1968 and its bloody end when the Soviet tanks rolled in; the rise of Solidarity in Poland in 1980; and in 1989, the collapse of Communist governments, mass emigration from East Germany and the election of Vaclav Havel as president of Czechoslovakia.

After the music, Havel came on the television screen and the loudspeakers at the Capitol with a special videotaped message in excellent English: "I am greeting you from a country which has just won its freedom, a country which is learning what freedom is."

It would be hard to find any message more calculated to make an audience appreciate the meaning of July Fourth, but both featured singers made an effort. After singing "I Got Rhythm" with some some well-calculated scatting on her top notes, Maureen McGovern sang "Give me your tired, your poor," the verses inscribed on the pedestal of the Statue of Liberty, as set to music by Irving Berlin. Estes dedicated "Climb Ev'ry Mountain" to Havel, Nelson Mandela and Martin Luther King Jr.

"Each of these great men had a mountain to climb," he said, "and they climbed it without bitterness."

He sang it not only with a great voice but with great conviction. And when the audience went wild at theend of his "Ol' Man River," he responded simply, "Thank you. You are very kind ... as America is."