Silvia Marcovici's debut with the National Symphony Orchestra last night in the Kennedy Center riveted the eyes of the audience on the slender young Romanian violinist.

She was draped in a navy chiffon gown, her violin nestled against her bare left shoulder, coal-black hair handing halfway down her back. No violinist in memory has done as much footwork while playing as she. During intense phrases she paced about an area three times that ever used by Jascha Heifetz. pAt other times, her foot solidly rooted to the stage, she swayed as if in a high wind.

All this happened during the Lalo "Symphonie Espagnole" which received a so-so performance. Marcovici has a subperb bowing arm that produces a wide variety of colors. Her left hand is agile, offering generally secure intonation. But the final impression was of somewhat gypsy-like playing with all the customary rubatos and flashing high notes, but nothing that could be called patrician or elegant. The orchestral accompaniment had much the same flavor, with its full share of roughness.

Mstislav Rostropovich, back for his winter stint with the orchestra, opened the evening with "Fanfare for Alexander" and "Variations and Song," both by Andreas Makris, the NSO composer-in-residence. The fanfare had all the triumphant blare of an M-G-M blockbuster. It made you look to see if Alexander of Macedon was coming down the aisle. Alas, he was not. The "Variations and Song" begins with some eloqent lyrical episodes, moves through some ingenious sonorities and rhythms and ends up like a latter-day "Caucasian Sketches."

The program closed with the first National Symphony performance of the Third Symphany by Dvorak. One of his earlier works, it has echoes of Schumann and cadences straight out of "Lohengrin." There is some original beauty, mostly in the slow movement, but less substance than the length warrants. On the whole, the orchestra played it very well. It may be music that cannot do any more than it did last night.