The line between Moscow and Washington was hot on Saturday night as the Moscow Philharmonic played in the Kennedy Center Concert Hall. Despite some of the worst traffic conditions ever to affect the Center, the hall was jammed, with many in the standing-room spaces.

In addition to the weather and traffic, demonstrators outside the Center were passing out statements protesting the Soviet Union's treatment of its Jewish population. Others were offering concert patrons a statement from Mstislav Rostropovich, music director of the National Symphony, whose sister, Veronika, was not permitted to accompany the orchestra on its current tour, though she has been a member of its violin section for over 20 years.According to Rostropovich, permission was refused her solely because she is his sister, and he has been stripped of his Soviet citizenship.

The orchestra is one of the USSR's top symphonic organizations. Its tone can shine with golden strings, solid brasses and matched woodwinds, all combining various characteristics of Russian players, notably in the horns, trombones and at times the oboe.

Dmitri Kitaenko conducted with an economy of gesture but great feeling, shaping the Second Symphony of Rachmaninov into long, expressive lines in which the orchestral sound was at its finest.

Throughout the symphony, the true glory of the orchestra shone with easy power, fine precision in the scherzo, and everywhere a sense of affinity.

Pianist Alexandr Toradze played the Third Concerto of Prokofiev, following a rather dry reading of Rimsky -Korsakov's Russian Easter Overture. The pianist, who won second place in last year's Cliburn Competition in Fort Worth, Tex.. is a great bear of a man who took over the famous concerto without a hint of effort.

In spite of its frequent performances, the Third Concerto is not the equal of any of the composer's other four, and more importantly, is not a good showpiece for a pianist, since it requires him to do a lot of something very near pounding. Toradze gave every indication of enjoying the combat, using some very strange physical mannerisms in his playing. Only his lyrical approach in the second movement approached anything like beauty.

The audience carried on after the concerto as if it had been played by Horowitz, Rachmaninov and Paderewski put together. It had not.