Sarah Caldwell and her Opera Company of Boston offered their capacity audience at Wolf Trap on Thursday night the most impressive performance of Verdi's "Aida" seen and heard here in more than three decades. p

Acting both as her own stage director and conductor, as she always does these days, Caldwell achieved her triumph by observing, for once, all the detailed directions Verdi gave both to director and conductor, and by urging her remarkable cast of singing actors to behave in the believable ways that Verdi also indicated.

The scenery of Helen Pond and Herbert Penn and the costumes of Ray Diffen had much to do with the way the great opera achieved its unusual impact. Making no attempt at the monumental effects often employed, Caldwell's team presented an "Aida" that looks like those Verdi knew and approved.

Shorn of its century of encrusted tableaux and massive groupings, this "Aida" presented an Egyptian population rushing around to hear the latest news about an Ethiopian invasion, and gathering later in excited triumph to celebrate their victory over the invaders. The precise placement of the principals, Aida, Amneris, and Radames as Verdi personally sketched their places on the stage greatly heightened the dramatic force of the music.

It was, of course, the music that made the most powerful impact, as it always must. The leading singers were superb actors who were equally impressive in their song. Shirley Verrett, having had the famous title role in mind for some time but not performed it until this production, sang with overwhelming beauty.

Easily dominating the largest scenes, her voice was often shaded down to the most exquisite pianissimos. This was an Aida who broke hearts with the passion of her pleas to Amneris and to her father, and, just as much, in the seduction of Radames that led him to betray his country. Repeatedly Verrett found the way to give long-familiar scenes new and poignant weight.

She was marvelously balanced by James McCracken, whose knowledge of Radames is complete and who sang with amazing vocal mastery, while conveying a feeling of human rationality to a part often emptily emoted. He took the end of "Celeste Aida" in the rarely observed pianissimo Verdi wrote, and the effect was, as Verdi knew it could be, magical. His part in the final duet was no less beautiful.

A newcomer in the role of Amneris, Elizabeth Connell from England came very near stealing the show with the splendor and excitement of her voice in the Judgement Scene, when she added to her singing a kind of frenzied, mounting fury that is specifically called for by Verdi, but that is rarely seen in most of today's statuesque singers. She was equally as effective earlier in her cat-and-mouse games with Aida. Her voice is sumptuous, subtly handled, and when she wants the sound, glorious.

David Arnold, a baritone from Boston, proved able to match his distinguished colleagues in acting and singing. His voice is not the largest, but it is well-focused with a ringing timbre, and more than enough, in combination with his forceful projection of the part, to win admiration.

William Dansby's King was suitably noble in look and sound. Only Ferruccio Furlanetto at times seemed tied to tradition in movement and to a mushy production that kept his fine bass from coming out in its best sound.

Elisabeth Phinney's Priestess and Michael Magiera's Messenger were well done. Special praise goes to the dancers, especially to the children, and to the acolytes who made the Consecration Scene the most intelligent and attractive in memory. The chorus was excellent, lacking the ultimate weight only in the Triumph Scene.

Caldwell and the orchestra worked beautifully together. The players produced beauty in sound with wide-shaded dynamic graduations so vital to this score. For the special lighting and stage effects of Gilbert Hemsley and others, and to the camel that brought down the house at the opening of the Nile Scene, further thanks. They all helped to bring us Verdi's "Aida" as he said he wanted it.