The Terrace Theater of the Kennedy Center, barely into its sixth month of life, will inaugurate this week what could be one of the most exciting new ventures in Washington music: chamber opera in an intimate theater.

On Tuesday nigh, John Mauceri, the music director of the new company, will open a six-week season with Mozart's "Impresario," the first half of a double bill that will then offer the Washington premiere of Weber's "Abu Hassan." The latter opera is one of four chamber operas that will have its local premiere during the next six weeks.

Mauceri has high hopes for the new venture. "It's a whole new feeling," he said recently, "to have your singers that close to the orchestra so that the clarient player, hearing a singer do a certain phrase, realizes that he is really playing a duet. The singers get to know the musicians in the pit and the whole thing is much more together than you even have in a big house."

Mauceri has spent plenty of time in "big houses." Among his recent successes was a performance of Wagner's "Rienzi" in San Antonio, the first production of the famous opera in this country in many years. A few weeks ago he conducted Puccini's "Manon Lescaut" in San Diego, then flew to Boston to conduct the Boston Pops Orchestra before coming to Washington for the opening rehearsals with the new Kennedy Center company.

With a pedigree that includes Beethoven's "Fidelio" at the Metropolitan Opera, and Verid's "Don Carlo," with the Welsh Opera Company, Mauceri will be one of the busiest conductors in Beverly Sills' regime at the New York City Opera this fall. There he will conduct Kurt Weill's "Street Scene," which he led in a triumphant revival last season, Massenet's "Manon," and Victor Herbert's "Naughty Marietta." Another of his major assignments there will be the New York premiere of Gian Carlo Menotti's newest opera, "Juana La Loca," which Sills sang recently in its premiere in San Diego, and will repeat in New York.

Mauceri, a Yale graduate, has been on the faculty of the Yale School of Music for 11 years. During his years there he was, for a time, conductor of the Yale Symphony Orchestra, which he led in a complete "Rheingold" by Wagner, and the U.S.premiere of the film score of "Der Rosenkavalier," that Strauss made some years after finishing the opera. With that orchestra, Mauceri gave the world premiere of the complete version of Charles Ives Three Places in New England. He also took the orchestra and the necessay chorus and soloists to Vienna where he led the European premiere of the Bernstein Mass.

When Mauceri talks about chamber opera, he looks at it through the eyes of a man who began, "with the very biggest, 'Mefistofele,' at the City Opera." Where Boito wrote for a huge chorus, added brass, and large orchestra, Mozart's "Impresario" is for three or four singers, depending on the edition, and a narrator. For the Kennedy Center performances, a new text has been written by Hugh Wheeler, the man whose "Sweeney Todd" recently won a Tony for Best Book for a Musical.

Wheeler is the latest addition to the long list of writers who have fiddled around with the libretto Gottlieb Stephanie wrote for Mozart in 1786, when Mozart composed the one-act hit in 2 1/2 weeks.

"The original text is os idiotic," Peter Ustinov said a few years ago when he made his own new version, "that I had to weep for my friend Wolfgang Amadeus Mozart." Last year when Sarah Caldwell produced "The Impresario" for her Opera Company of Boston, she wrote her own text.

Wheeler, however, has had the added pleasure of writing a new text not only for Mozart, but also for the Weber opera that will follow it. In completely logical sequence, "Abu Hassan" will be given by the impresario of the Mozart opera. Its story is one of nonsensical fancy right out of the "Arabian Nights." Both operas will be sung in English.

On Wednesday night, the new opera company will enter a different kind of dream world. Domininick Argento, a recent Pulitzer Prizr-winner, has set a fascinating libretto by John Donahue. The author best explains the story that is sung by seven singers:

"The scene is like a memory (1914), like an old postcard from a foreign land lshowing the railway station of Morocco or some place, hot and strange, like the interior of a glass covered pavilion or spa.

"There are entertainments present, a curious daytime floorshow for the benefit of the waiting guests. A puppet plan (done with very human-like puppets) is performed on a small covered stage at one side of the room. Around this room are scattered the people, some real, some not. Several move about on small wheels with cords which allow them to be pulled back and forth or pherhaps they just turn or jerk in position slightly.

"The live characters play more than one part. We see each one trying hard to protect whatever small part of himself he has in his suitcase, the symbol of his secret or lack of secret, his dream or lack of dream. It is through the actions of these waiting creatures that we see our own fears and anxieties along with the fierce way in which man protects himself from the stranger, his probing wish for company and comfort.

"Accompanying this little comedy is an Algerian orchestra which is ever present in costume and fez and seen through some cardboard ferns. By the look on their faces, they seem to have seen it all before and will see it again."

Composer Argento adds illuminating comments on someof the unexpected aspects of his score: "Somewhere toward the middle of 'Postcard From Morocco,' the onstage dance band entertains the waiting travelers with a medley of themes from Wagner's opera -- the sort ofmusical farrago one might expect to find aboard a ship, or at a spa, or in a foreign railway station restaurant around 1914.Among the various bits and snatches, the 'Spinning Song' from "The Flying Dutchman' occupies a central position. The selection is intended to conjure up more than local color: in 'Flying Dutchman,' Wagner's hero is doomed by supernatural forces to sail forever over the oceans, until, through a stranger's act of compassioand love, the curse is lifted and the journey ended.

"Postcard From Morocco' could in a way, serve as a prologue to Wagner's opera, suggesting a different but equally possible origin of that journey: not launched by supernatural forces at all, but by very human ones, by people who fail to show charity or pity, love or understanding for a fellow creature. . . ."

Not yet 10 years old, Argento's opera (recorded on Desto Records DC 71373/88) has become a notable example of the finest and most imaginative kind of operatic creation being done in this country. Like "The Impresario," it has been a hit since its first performance.

The Mozart-Weber double bill will alternate with Argento between July 10 and 29. From July 31 through Aug. 19, they will replaced by offenbach's "Christopher Columbus," and Donizetti's "II Furioso all'Isola dis San Domingo," of which more later, as for instance on July 29.

Audiences in the Terrace Theater in the next six weeks will have the pleasure of hearing unfamiliar chamber opera of high promise in a setting that should be ideal. To the new company, break a leg! CAPTION: Picture, Faith Esham in "Abu Hassan." By Harry Naltchayan - The Washington Post