The young American violinist who won a gold medal in Moscow's 1978 Tchaikovsky Competition, Elmar Oliveira, played a rich program last night at the Library of Congress.

Oliveira's sound is particularly sumptuous at the bottom of his instrument. He drew tone of considerable size and resonance from the G string, especially in Ernest Bloch's first sonata, with its great leaps from the top of the register to the bottom, and its soulful and agitated melodies from the violin's equivalent of the contralto range.

Throughout the evening Oliveira seemed to be focusing on those lower sounds. Though his command of the violin seemed quite assured regardless of range--with virtually no pitch or tonal discrepancies--there was a special vibrancy on the lower side. It was partly because his bowing arm seems especially strong in that trying position and also because his high tones on the E string don't shimmer like those of, say, Stern.

Another work on the program that dotes on the G string was the brief C Minor Sonatensatz of Brahms; in that work Oliveira also displayed an impressive rhythmic precision, especially in its accented offbeats.

The Beethoven A Major sonata, Op. 30, No. 1, was gracious in its own way. But, heretical as it may sound, this work--in the hands of any artist--strikes this listener as dull. Beethoven was one of the protean figures in the history of the arts, but he had his lesser moments, and this is one of them. The melodies are predictable and the music fails to go anywhere of special interest harmonically. Give him a C for effort. Oliveira played it safe.

The last two works had bravura flair. One, a Cantabile by Paganini, was a stirring piece of lyricism. And the other, a Spanish dance by Sarasate, was full of zing.

Pianist Robert McDonald was impeccable but had little opportunity for adventure.