The Vienna State Oprera opened its first visit to the country with brilliant strength on Saturday night when Leonard Bernstein conducted Beethoven's "Fidelio" in the Kennedy Center Opera House.

With the Vienna Philharmonic spreading glory from the orchestra pit, Bernstein underscored all the dramatic tension and power of Beethoven's only opera. The light banter with which the first scene begins was as infectious as the torrent that closed the Third Leonore Overture -- but always with the hint of the sinister developments that follow so soon after.

The first passage of unparalleled greatness in "Fidelio" comes with the introduction to the Canon Quartet. This took on an aural radiance Saturday night that spread upward from the lower strings to the four singers, providing the rapture that is unique to that moment.

Bernstein placed the Third Leonore immediately after the duet between Florestan and Fidelio, at the moment her husband's life and freedom became assured. It is a logical solution to the longstanding question of where to use that overture. Unfortunately the audience's applause obliterated the opening of the overture, while flubs in lighting robbed it of some of the intended effect.

The mounting impact of the performance was the obvious result of a clearly unified view of the opera held by Bernstein and stage director Otto Schenk. The motionlessness of the four singers during the introduction to the canon quartet was as impressive as the inner ferocity vividly projected by Theo Adam's Pizarro.

Many times at crucial moments, the actors moved in perfect synchronism with the music, heightening the effect created by director and conductor. The climax of the confrontation between Fidelio and Pizarro, with its offstage trumpet calls, came off just right.

There is quite a bit of spoken dialogue in "Fidelio," much of it rather intimate in character. It is thus appropriate for it to be done on a conversational level. But some of it was rather too quite, and the great line, "Ah, meine Leonore, was hast du fur mich getan?" was not heard at all.

Aside from the lighting, everything seen matched and enhanced what was heard. The sets by Gunther Schneider-Siemssen are superb in the way they convey a sense of the meneace and terror that lurks in the drama. At the end, the lowering of the huge drawbridge is a thrilling symbol of the release of the prisoners to their waiting families.

The cast was strong, troubled in only one respect. Lucia Popp is an ideal Marzelline both in acting and exquisite singing. Kurt Rydl's Rocco, magnificently voiced, is also powerful in its relationships with the other principals. Adam is a stunning Pizarro, a singing actor whose whole appearance mirrors the vicious hatred that eloquently pours out of his voice.

Jess Thomas made one of the finest openings in memory with that wrencing cry, "Gott! Welch dunkel hier," for which no tenor ever thanks Beethoven. He started the "Gott!" softly and then let it open up in moving style. If the final ravings of his first aria sounded cruelly tight, so they do from nearly everyone who sings the role. He continued strongly.

Gwyneth Jones is a problem. She acts marvelously as Fidelio/Leonore. In scene after scene she was completly convincing. But her voice continues to evade her best efforts at control, and for as much of the time as she was right on pitch, her strong overdrive forced her into severe sharping. It is a problem that unfortunately spoils much of the music.

Horst Laubenthal sang beautifully as Jacquino, as did Hans Helm as the Minister, and the two prisoners, sung by Karl Terkal and Alfred Sramek, were usually effective.