Andrew Lloyd Webber's "The Phantom of the Opera" is stalking the Washington benefit circuit -- and the committee members of 20 charities think it's just the right spirit.

If you aren't a season subscriber, it's beginning to look as though the only sure way to get a good seat is to go to a benefit.

The romantic musical, with all its elaborate sets, props, magical devices and full orchestra, will be performed in the Kennedy Center Opera House beginning May 28. Already, "Phantom" has broken a box office record by selling $367,000 worth of tickets the first day they went on sale here. So far more than 80 percent of the tickets for the show's scheduled 14-week run have been sold.

The really dramatic "Phantom" party is the Kennedy Center's own 20th anniversary gala, its firstannual benefit and the first onstage. The 2,226 expected guests -- depending on the price of their tickets -- will party before, during and after the May 29 performance, on and under the adjacent Eisenhower Theater stage.

Those paying the top ticket prices will be invited to go down through the trapdoor of the stage to the Phantom's World -- the legendary stagehand's universe. They can raise Hades (or a polite equivalent) amidst a miasma (produced by dry ice), cages full of rare papier-mache beasts, chairs on which famous actors have sat, backdrops from well-remembered productions and some things impossible to identify.

A $250 ticket buys -- in addition to drinks and premium orchestra seats -- a seated dinner onstage after curtain calls, and dancing afterward in the underworld. Shades of last year's multiple-charities benefit at the Departmental Auditorium starring Princess Di -- the cast will appear only at the seated dinner.

For those who have seen enough of the cast on the stage and don't mind eating while standing up, the price is $50 less.

Those whose needs are satisfied by drinks and a bite before the show can pay $150 and still get orchestra or first-tier seating.

People who are happy enough to eat and drink at home, but want to see the show and benefit the center, can pay $80 for second-tier seats.

Jane Sloat is chairman of the center's "Phantom" benefit, and, it sometimes seems, of everything else. (She's also chairman of Entertaining People, which closes today at the Mayflower Hotel.) Her husband has threatened to lock her in one of the cages beneath the stage if she takes on another benefit this month.

"This is not just another social evening, but a cause," James D. Wolfensohn, Kennedy Center chairman, told the benefit committee members over cranberry-nut bread and coffee a while back. "The Kennedy Center isn't bankrupt but it is impoverished. We're poor but we have big dreams." The benefit profits will go to artistic, educational and public service programming.

Though the Kennedy Center has first dibs on the "Phantom," the ghostly presence will benefit 19 other organizations. Children's Hospital (May 30) and the Easter Seal Society for Disabled Children & Adults (June 1) are the only others to buy up the whole house, though D.C. Hotline has taken 1,000 seats for the June 1 matinee.

Sixteen other organizations have bought smaller blocks of tickets for their members: House of Mercy, Duke University, Myasthenia Gravis Foundation, Edmund Burke School, Jewish Council for Aging, Episcopal Center for Children, Volunteer Clearing House, Temple Beth Ami, Washington Opera, Coalition for the Homeless, Greater Washington Chapter of Brandeis University, Northwest Kiwanis Club, Prince George's Opera, College of Notre Dame and Davis Memorial Goodwill Industries.

Say you can't afford to benefit anybody but still want to see the show. It can be done -- provided you are lucky enough to snare a stray seat. August offers the best chance.

By decree of the New York "Phantom" organization, no discounts on tickets are given to groups, charity or otherwise. Tickets for regular performances sell for a top price of $55 and a bottom of $12 for standing room only at a matinee.

There is absolutely no truth to the rumor that Opera House seats under the Phantom's chandelier will be cheaper -- they're the best seats.