Oxana Yablonskaya is a Russian pianist who emigrated from the Soviet Union to this country two years ago. She now lives in New York City, where last year she made a tumultuously successful debut.

On Saturday afternoon she played at the Kennedy Center, opening this year's Piaino Series for the Washington Performing Arts Society. A pupil of the teachers of Vladimir Ashkenazi and Lazar Berman, the elegant-looking pianist chose a heavy program with which to state her case in her initial Washington appearance: Beethoven's Sonata in D Minor of Opus 31; the Chopin B Flat Minor Sonata; the Third Sonata by Prokofiev, and Mussorgsky's "Pictures at an Exhibition." These were prefaced by a poetic reading of the Sgambati arrangement of the D minor melody from Gluck's "Orfeo."

Early in the Gluck, Yablonskaya demonstrated her remarkable gift of producing a pianissimo singing tone of exquisite quality, something to which she returned with fine effect in the trio of the Chopin Funeral March. There are no serious technical problems for Yablonskaya -- there could be none for anyone of her generation with her pedigree who went on to become a teacher at the Moscow Conservatory.

At the same time, there were matters that recurred in her playing that created problems both in interpretation and in making clear the content of the large works on her program. Aiming for large effects, she often blurred expert finger work with over-pedaling, and some of the vital passages of both Chopin and Mussorgsky were seriously marred by her frequent tendency to rush. The Beethoven was well laid out, but Yablonskaya's habit of extreme deliberation in placing certain notes approached the mannered in the slowest pages.

A highly understandable fatigue may have set in by the time she reached the Mussorgsky. For whatever reason, many notes came out wrong, and, in the increased pounding, things became more than a little splotchy.