Well into a season often paved with good intentions, the Washington Opera finally offered musical drama of the highest caliber last night. It would be difficult to overpraise this revival of Dominick Argento's "Postcard From Morocco," and it is impossible to imagine a more sensitively sung and acted, more shrewdly directed or more ravishingly designed production than that which was cheered by a sold-out audience at the Terrace Theater.

There is little plot in this 1971 work, full of barely unraveled dramatic threads from a rich tapestry of which the audience sees only a swath. It is about those intimate truths, fantasies and lies which we share only with POSTCARD, From D1> strangers. It is about the careful guarding of secrets and possessions, and about privacy, privation and loneliness. Most of all lonliness. Seven travelers wait for a train in a station in some faraway, exotic land. The content of their luggage is as much an enigma as the stories of their past, and they taunt each other with the kindness we too often reserve for strangers. a

This existential tapestry is embroidered with some very derivative music, but more on that later. What matters is the inventiveness with which Argento treats not only the voice, the instrument he obviously loves best, but also the nine other instruments making up the strikingly varied ensemble. And what matters even more is the sheer beauty of the vocal lines.

With one exception, the cast was the same as that of the 1978 Kennedy Center Summer Opera production, and in every way it surpassed the fondest memories of that season. Dennis Bailey recreated his powerful protrayal of Mr.Owen, the only passenger with a name. Where he once had problems with dynamic control, last night he gave a powerful, less stentorian and fully mature interpretation of a man with a dream. Elaine Bonazzi's Lady With a Hat Box was a musical and dramatic picture of capricious frumpiness, making her transformation into the Foreign Singer a fantastic revelation, using sensuous movements and a tenor's timbre while singing a torch song of nonsense syllables.

Claudette Peterson's voice was all clarity and crystal for the Lady with the Hand Mirror and the Voice of the Opretta Singer, shining through the opening septet with the freshness of morning dew. Wayne Turnage and William Dansby provided the darker vocal colors, with Dansby still often veiling his rich voice, as the Man With a Shoe Sample Kit and the Man With a Cornet Case. As the Lady With a Cake Box, Barbara Hocher's scena provided one of the evening's most gripping moments, a mezzo lament reminiscent of some of the vocal writing of Henze via Weill.

The one variation from the original cast was a welcome Washington Opera debut. Michael Hume played the Man With Old Luggage with commanding delicacy. He is blessed with a distinctive lyric timbre, reminiscent of a young Peter Pears but without Pears' controversial forward vocal placement. His first monologue was sung as a dirge of hidden sweetness and rage, with beautifully floated top notes and smooth shifts into head voice when so desired. His blend with Turnage's carefully colored baritone was as unforgettable as that of the short duet between Hocher and Peterson.

Much could be said about the fact that most of Argento's melodic effects are borrowed from Wagner or other composers. Audiences familiar with opera will recognize the sources, others will be perhaps more taken by the opera's undisputable impact. Suffice it to say that its musical accessibility and John Donahue's impressive libretto would be enough to lift "Postcard From Morroco" from the ordinary. When you add Argento's unique gift, that of setting American English to music so naturally, the work can be seen as an operatic treasure. And it is not likely to ever be as treasurable as in the Washington Opera Production, designed by Zack Brown.

"Postcard From Morroco" will be repeated on Jan. 9, 11, 13, 15 and 17.