Giuseppe Verdi is extraordinarily well served both in music and drama in the Washington Opera's new production of 'Un Ballo in Maschera," which opened the company's most ambitious season of date at the Kennedy Center on Saturday.

This great work of Verdi's middle years in triumph of all the operatic arts: conducting, singing, staging, set design and costuming. The decision, made by director Frank Rizzo, to set the opera in "a northern European kingdom at the close of the 18th century" conforms with Verdi's intent, but does away with the problems involved in setting it either in the court of Sweden's Gustav III or the other usual alternative, colonial Boston.

Each time the curtain rose on the handsome new production, a gift of the Gramma Fisher Foundation, the stage picture was an ideal realization of Verdi and Somma's work. The king's chamber, the house of Ulrica the fortune-teller, the gallows ground and the grand hall of the king's palace, each in superb styling, were designed to permit Verdi's work its best surrounding. The sets and costumes, the work of Zack Brown, cannot be over-praised.

Even before the rise of the first curtain, conductor Cal Stewart Kellogg has established a muscial atmosphere that was to persist throughout the performances. With an enlarged orchestra that gave Verdi's magnificent writing every nuance in dynamics and dramatic intensity, Kellogg proved himself a high-powered musician of impeccable taste and ability.

And the singing! Teresa Zylis-gara, already known in Verdi for her Desdemna, sang with great ease and beauty of tone. She has the style perfectly in hand and, as she moved through the role in Amelia, singing it for the first time, she was ideal in sound and movement. Inevitably as she grows in the part she will add subtleties that will further enrich her portrait. There can be more use of pianissimo and more precise sculpting of certain great lines, where she can highten still more the tragic pathos of the moment. But she is a beauty to watch and hear in a role that perfectly suits her.

Then there is a new tenor -- new to this country, but destined to be well known and fervently admired in a short time. Making his U.S. debut as Riccardo, the king, the Bulgarian Michail Svetlev is -- mirabile dictu! -- slim and handsome as well as blessed with a rich, solid lyric tenor that comes out unforced, handsomely shaded and handled with real style. The mounting fire of the great second act duet with Zylis-Gara marked Svetley as a treasure even in today's world, where there are several first-class tenors. He has a slight tendency to slide from one note to the next, which, with the hints of sobs in the last act, he would be better off without. But very high praise goes to this welcome new star.

Mariana Paunova, who has been admired here in baroque opera, won instant admiration from the very first phrase of her great scene as Ulrica. She colors her voice richly, not hesitating to make vibrant use of the heaviest chest tones. But she does it in a way that adds to the characterization without ever marring a voice which is impressive from top to bottom. Her acting, too, was particularly well done in a scene that has often been little more than a caricature.

Leo Nucci, singing Renato, displayed a strong lyric baritone which he uses with excellent effect. The voice is well focused, somewhat reminiscent of Giuseppe Valdengo. If Nucci does not find wide vocal subtleties, his acting is full of dramatic tension.

Janice Hall walked out his high honors as the coloratura Oscar, singing brilliantly and looking as well as anyone can in that trying part. Harry Dworchak and William Powers were estimable as the two officers, as were Marvin Finnley and Calvin Remsberg as Silvano and a magistrate, while David Perry succeeded in bringing a strong touch even to the brief role of a servant.

Then there was the chorus! Now under the tutelage of Norman Scribner, its singing on and off stage was a marvel of what operatic choral singing can be, not merely in sound but with enunciation and changing color that contributed directly to the whole.

With beautiful lighting by Patricia Collins that would have been beyond praise except for troublesome moments when something goofed, the entire evening was an unbroken triumph. What a great way to open a season!