BARNUM: produced by Judy Gordon, Cy Coleman, Maurice and Lois Rosenfield, in association with Irvin Feld and Kenneth Feld, with music by Cy Coleman, lyrics by Michael Stewart, book by Mark Bramble, directed and choreographed by Joe Layton, scene design by David Mitchell, costumes by Theoni V. Aldredge, lighting by Craig Miller, sound by Otts Munderloh, orchestrations by Hershy Kay.

With Stacy Keach, Dee Hoty, Catherine Gaines, Terri White, Bobby Lee, Gabriel Barre.

The opening number of the second act of "Barnum," which opened a six-week run at the Kennedy Center Saturday night, is perhaps the quintessential moment in this hyperkinetic musical.Musicians come tootling down the aisles. P. T. Barnum appears dressed in a clown suit and showers the audience with handbills. Within minutes there are 15 people onstage playing, singing, jumping, running, urging us to "Come Follow the Band." There is a lot going on -- but all the commotion goes nowhere.

"Barnum" is desperate top entertain. With a frenzied urgency, it practically gets down on its knees and begs us to have a good time -- and sometimes it succeeds. The audience is assaulted with action, starting from the very moment it enters the theater, with clowns dashing about the aisles (and one walking along the ledge of the Opera House lobby), continuing with a stream of excessively loud, fast music, scene changes and acrobatics. The musical is rather like a clown -- if one stunt fails to amuse, it quickly tries something else, never giving up any possible effort to entertain.

The story revolves around the central character of P. T. Barnum (1810-1891), the legendary showman who, as one biographer put it, saved "America from acute solemnity" with exhibitions and shows starting with a 161-year-old slave who purported to be George Washington's nurse. The biographical details in the musical are, by and large, bunkum, which, I suppose, is poetic license appropriate in a story about a man who virtually defined the word "humbug."

The structure of the show, which has been playing on Broadway since April 1980, hangs on the conflict between Barnum and his wife, Charity, or "humbug versus truth, flimflam versus fact." Barnum is portrayed as the magnificent dreamer, a man who wants vibrant "colors" in his life instead of blacks and grays, while his wife beseeches him to have "sensible dreams" -- a theme rather prevalent in Washington theaters these days, with "God Bless You, Mr. Rosewater" at Arena Stage and the somewhat similar "Verdict" at Olney Theater. What she calls "lies" are to him "rosy possibilities."

"Barnum" moves from P.T.'s escapade with the ages slave to the establishment of the American Museum, the promotion of Tom Thumb, Jumbo the elephant, Jenny Lind, Barnum's brief involvement with politics and the start of Barnum and Bailey's circus. "The Greatest Show on Earth." The scenes are knitted together with circus interludes, juggling clowns and acrobats, and the circus metaphor infuses the entire production. It even continues through the intermission, with hucksters in the lobby selling tote bags and T-shirts emblozoned with Barnum's maxim "There's a sucker born every minute" -- and at those prices, whoever buys one deserves to wear it.

It's a production that must be borne, like a pyramid of acrobats, on the shoulders of whoever plays Barnum, and Stacy Keach, who is overall quite wonderful, unwittingly presents a clue to a fundamental problem with the show. At one point he is supposed to walk a tightrope stretched across the stage to a perch in which sits Miss Jenny Lind -- another metaphor about the supposed relationship between them. On opening night, Keach tried twice, but failed to get across the tightrope -- but his efforts were real and involving, in a way the clockwork production around him fails to be. For a moment, we were allowed to focus on one thing, and we really wanted him to get across that rope.

The rest of the time we are too busy to care. Things are constantly being thrown at the audience -- balloons confetti, handbills and noise. The amplification system is turned up so loud that it is almost painful at times, and occasionally you feel like the performers are grabbing you by the lapels and shaking you and screaming "LIKE ME! THIS IS FUN!

Keach is adept at batting out the patter songs, which are a generation removed from "The Music Man" verbally, but musically less interesting. Cy Coleman, the veteran composer of such hits as "Sweet Charity" and "Seesaw," has given this production one particularly lovely song, "The Colors of My Life," and one other pretty one, "Love Makes Such Fools of Us All." But the rest, like the show, seem to be one long production number.

Keach seems to be genuinely having a good time, from his first entrance, an unashamedly ham-bond blast, to his final spotlight. He has the charisma and the athleticism the part requires (surely he'll get across the tightrope some night); the only drawback is that we are left thinking about how hard he's working rather than reveling in being seduced. Dee Hoty as Charity sings beautifully and looks beautiful, and acts like a robot with programmed responses and facial expressions. Chatherine Gaines is fine as the shapely Lind, and among the supporting cast of multi-talented performers Terri White is a standout with a beautiful belting voice and almost equally dexterous dancing; one looks forward to seeing her in a bigger part in another show. She is one performer who would seem not to need the amplification. Bobby Lee as Tom Thumb is another who can sing and dance with equal proficiency.

In the end, "Barnum" is just too aggressive a musical, making up in energy what it lacks in plot. There are too many stunts, sequins, trumpets, feathers, trapezes, twirling batons, backbends and flashing lights and too much flying hoopla. One man in the audience was asked by a friend in a neighboring row how he liked the show. "I love it," he said. "I don't have to think."