Wolfgang Amadeus Mozart could do almost anything in music, but there was one skill that he never really mastered. In his (too brief) years of maturity, he had trouble composing operas that were single-mindedly comic (like "The Barber of Seville" or "Gianni Schicchi") or uncompromisingly tragic (like Gluck's "Orfeo"--or anyone else's). In his quizzical awareness of life's complexity, he resembles William Shakespeare.

Is "Don Giovanni" tragic or comic? The only possible answer is "Yes," as it is, less obviously, for "Cosi fan tutte" or "The Marriage of Figaro," where some of the farcical characters have a disturbing habit of turning into real people suffering real pain. Even in the crazy, mixed-up "Magic Flute," there lies behind all the nonsense a message as serious and as seriously stated as that of Beethoven's Ninth Symphony--which has essentially the same message, the brotherhood of humanity.

Those who wonder how Mozart got that way can find some clues--or observe him on the brink of his breakthrough--in "The Abduction from the Seraglio," which had a splendid opening night Saturday in the Kennedy Center's Terrace Theater. "Abduction" is not performed nearly as often as it deserves--partly, perhaps, because the composer was still on the brink of his final greatness when he composed it but more likely because some of the music is terrifying to singers. The Washington Opera's production is fully worthy of this masterpiece, coping cleverly with its tricky stylistic problems and giving a clear glimpse of its greatness.

There are really two operas in "Abduction," and they can be distinguished much more clearly here than in Mozart's later operas. One is a serious opera with serious music about young lovers who are separated by a cruel fate (pirates and captivity in this case) and spend the entire evening alternating between hope and despair. It is hardly a new idea; in fact, it dates back at least to "Daphnis and Chloe," which was written some 17 centuries ago. The "Turkish" flavor and milieu were no more original; Turkish subjects, and particularly stories about escapes from harems, were commonplace in Europe at the time--nowhere more than in Vienna, where a Turkish army had been turned back two centuries earlier. Mozart's treatment would not have survived for the current 200th anniversary production, except that the story serves as a pretext for some very beautiful music.

The other opera contained in "Abduction" is a bit of comic fluff about how to rescue two captive European women from a Turkish harem. It includes exotic pageantry, with marching janissaries in colorful costumes carrying very long spears; comic business about how to drug the harem's chief guardian and sneak away while he sleeps; and a good drunk scene (complete with drinking song), given added spice by the fact that one of the drunks is a Moslem and theoretically a teetotaler. Also some fine sight-gags involving a ladder and a balcony in the dark of midnight, a bit of gallows humor when the captives are threatened with exquisite tortures and a few pungent episodes in the battle of the sexes. Above all, in the character of Osmin, it has a comic villain whose full potential can be realized only by a singing actor of epic abilities--someone like Ronald Hedlund in the present production.

For its full effect, "Abduction" requires singers who can excel in the kind of florid, acrobatic vocal lines that Mozart once called "chopped noodles" in a letter to his father. "Too beautiful for our ears, and an enormous number of notes, my dear Mozart," said Emperor Joseph II after the first performance of "Abduction." "Only as many as are needed, Your Majesty," Mozart replied politely but firmly. Posterity has endorsed Mozart's opinion, but in fact the vocal notes do outnumber the words of the text by several orders of magnitude. This, musically, is both the glory and the challenge of the work--a challenge that primarily confronts Constanza (soprano Karen Hunt), Belmonte (tenor Gregory Kunde) and Hedlund in the role of Osmin. Each of them meets it with superb style and generally excellent singing, though on opening night all three had a few insignificant moments of discomfort--Hunt and Kunde on high notes, Hedlund on low ones.

The work's humor is shared by Hedlund with soprano Kathryn Gamberoni (Blonda) and tenor David Gordon (Pedrillo), both of whom show a fine comic flair. Their singing assignments, though less daunting than those of the principals, are both varied and demanding, and they are filled, on the whole, with distinction. As is becoming traditional in productions of the Washington Opera (particularly those in the Terrace, with its ruthlessly clear acoustics) the ensemble singing is polished to a high gloss--a most important point in Mozart's music.

The high quality of acting throughout the cast is epitomized by the performance of Michael Tolaydo in the non-singing role of Pasha Selim, a rather problematic character whose quixotic kindness brings the plot to an improbably happy conclusion. He solves the dilemma by playing Selim as a sort of Turkish Hamlet, with a style reminiscent of Ronald Colman. Here is an Oriental potentate who has obviously been to a good British school. It works.

Other elements that work include the splendidly atmospheric sets and costumes by Zack Brown, an artist whose talent takes special inspiration from budget limitations. They evoke precisely the serio-comic mood of the production. The stage direction is by Donald Saddler, who also collaborated with Brown in the staging of "On Your Toes" and whose background is mostly in choreography. For this work, with its two sharply contrasting styles, he was an inspired choice. The serious moments are staged in the traditional style, which is rather static but was obviously what Mozart expected. The comic sequences, however, are full of brisk, well-coordinated motion, much of which also helps to fill in details of background that are only implicit in the words and music. Notable in this respect is the way Osmin picks the fruit from two potted fig trees in the first scene while he studiously ignores Belmonte's attempts to catch his attention. He is carried from one tree to the other, at shoulder height, by three slaves so that he can pick the figs effortlessly and drop them into a basket carried by a fourth slave. A whole culture is characterized in the process.

Enjoyment of the production is considerably enhanced by hearing it in English. Andrew Porter's fine translation comes across with beautiful clarity in the singers' carefully pointed diction. Conductor Gerard Schwarz, who is making his operatic debut in this production, gives it an idiomatic style and pace, though on opening night the orchestra's string tone sounded slightly undernourished. He established effectively the ensemble spirit that, more than any individual performance, makes this an outstanding production.