Last night in Tysons Corner, soprano Chrissellene Petropoulos embodied the role of Despina, the worldly-wise maid in Mozart's "Cosi fan tutte" who slyly advises the two heroines on how to practice "all the little artifices that ensnare lovers."

A few minutes later, she was Fiordiligi from the same opera, striking dramatic poses and singing in heroic tones, with larynx-jarring leaps and roulades, about her unshakable fidelity to her fiance'.

After the intermission, she was Tatiana in Tchaikovsky's "Eugene Onegin," an impulsive, infatuated teen-ager pouring her heart into a letter and offering herself totally, in joyful hope and anguished fear, to a man she had met only a few hours earlier.

The occasion was the season's opening concert by the Virginia Chamber Orchestra in a ballroom of the Sheraton Premiere Hotel. With a program that included three vocal numbers ("Una donna a quindici anni" and "Come scoglio" from "Cosi" and "The Letter Scene" from "Onegin"), conductor Andrew Litton allowed his guest artist to dominate the stage through most of the program -- though the orchestra alone was quite impressive in the overture to "Cosi" and Beethoven's "Leonore Overture No. 1." .

While it yielded the spotlight gracefully to Petropoulos most of the time, the orchestra did occasionally cover her voice, particularly when she was singing in her lower register. The concert was not flawless but it was absorbing, and tonight's repeat in the Washington Street United Methodist Church in Alexandria is worth catching.

The "Onegin" scene alone is as demanding a quarter-hour as a soprano can face. Add the two sharply contrasted Mozart numbers, and no singer alive can do equally well in all three arias.

The chief assets Petropoulos brought to her assignment are a bright, powerful and well-focused upper register and acting skills that are impressive even in the relatively restrained medium of a concert stage. Her chief problem, to judge by last night's performance, is a lower register that lacks the power and clarity of her head tones -- that and a still incomplete identity with the role of Tatiana.

She was most clearly successful in Despina's aria, with which she began her evening's work. In "Come scoglio," the music's formidable technical challenges posed no serious problems but the singer seemed less assertive, less identified with the role.

As they did last season in the "Posthorn" Serenade, Litton and his orchestra again showed a special affinity for Mozart. Beethoven's overture is the least effective of the four that he wrote for "Fidelio," and the idiomatic, alert performance did not disguise this fact.