Musical theater, popular and classical, will be the specialty this summer at Wolf Trap Farm Park, according to the season schedule announced yesterday.

To replace the Metropolitan Opera, which is moving to the Kennedy Center after several seasons at Wolf Trap, there will be productions by four opera companies, as well as a new Wolf Trap production of "Brigadoon" hopefully aimed at Broadway, a revivall of a Sousa musical and a special tribute to the late Richard Rodgers.

A heavy emphasis on classical music will be reinforced by 16 National Symphony Orchestra performances, including a Rostropovich family weekend on July 18-20 in which Mstislav Rostropovich will conduct his two daughters and sons-in-law (two pianists, a violinist and a cellist) in various concertos.

Dance and popular music will be relatively de-emphasized, but July performances by the Joffrey Ballet and The American Dance Machine have been scheduled. A five-day jazz festival will span the July 4 holiday, and special programs will be devoted to blue-grass, country music, big bands and "Sensational Singers of the Sixties." Perennial favorites such as Virgil Fox, Chuck Magione, Pete Seeger and Arlo Guthrie, the Preservation Hall Jazz Band and Dionne Warwick will return throughout the season.

Four evenings of chamber music will be presented by The Concert Soloists of Wolf Trap under the direction of Earl Wild, and the New York Philharmonic will give several performances.

Opera companies performing at Wolf Trap will include: in June, the Opera Company of Boston, whose director Sarah Caldwell is the Wolf Trap music director; in July, the New York City Opera, whose general director Beverly Sills is the Wolf Trap deputy program committee chairman; in August, the Greater Miami Opera, with a new production of "Die Fledermanus"; and the Wolf Trap Opera Company with a midnight performance of Heinrich August Marschner's "The Vampire" on June 27.

A highlight of the New York company's visit begins July 26 with its production of Kurt Weil's "Silverlake" ("Das Silversee"), which will have its American premiere in New York next month.

Sills announced that the New Yorkers will also present their new production of "Don Giovanni" and a "Barber of Seville" in which she will "be singing Rosina for what I hope will be the last time."

For the Boston company's production of "Aida" (beginning June 12), Caldwell said "I've promised Mrs. Shouse an elephant. I'm not sure what the elephant will do yet, but I'm sure it's good casting." Also coming to Wolf Trap from Boston will be a new "Madame Butterfly" beginning June 13, which Washington will hear for the first time in Puccini's original version, and a new "Flying Dutchman" beginning June 14.

The final stage production will be a revival of John Philip Sousa's "The Free Lance" starting Aug. 25 starring John Reardon, and trumpeter Al Hirt will close the season on Aug. 31.

There are still some gaps in the announced schedule -- for example, the gala on June 3, whose chairman Elizabeth Taylor Warner, was unable to attend the press conference. Program committee chairman Mrs. Jouett Shouse said that the season will be extended to 15 weeks, beginning in mid-May, but no activities for May were announced.

Also unannounced was the identity of a Russian dance group which had been expected to come to Wolf Trap but has been canceled or of an international company which is being sought to replace them.

Craig Hankenson, executive director of the Wolf Trap Foundation, said that "The Russians decided to go to Afghanistan instead of Wolf Trap."