Each high note had the crowd in ecstasy so that it stopped the show midway in the ``Mad Scene,'' but the real reason was a realization of the extraordinary performance unfolding at the moment. Miss Sutherland appeared almost as another person in this scene: A much more girlish Lucia, a sensational coloratura who ran across stage while singing, and an actress immersed in her role. What followed the outburst brought almost breathless silence as Miss Sutherland revealed her mastery of a voice probably unique among sopranos today.

This big, flexible voice with uncommon range has been superbly disciplined. Nervousness at the start must have caused the blemishes of her first scene, or she may warm up slowly. In the fullness of her vocal splendor, however, she could sing the famous scene magnificently.

Technically it was fascinating, aurally spell-binding, and dramatically quite realistic. Many years have passed since a Metropolitan audience heard anything comparable. Her debut over, perhaps the earlier scenes will emerge equally fine.

The performance also marked the debut of a most promising young conductor, Silvio Varviso. He injected more vitality into the score than it has revealed in many years. He may respect too much the Italian tradition of letting singers hold on to their notes, but to restrain them in a singers' opera may be quite difficult.

Richard Tucker sang Edgardo in glorious voice. His bel canto style gave the performance a special distinction. The remainder of the cast fulfilled its assignments no more than satisfactorily just as the old production and limited stage direction proved only serviceable.