"Slava! Slava!" shouted the Oratorio Society of Washington, last night in the Kennedy Center Concert Hall. On the podium, the conductor nicknamed "Slava," Mstislav Rostropovich, responded vigorously. He ran the volume up a few more notches, whipped into an even more frenzied tempo and spurred the substantial percussion section to greater bursts of energy.

It was not an ego trip for the man whose nickname is the Russian word for "glory." "Slava" is written in the script, repeatedly, in Modeste Mussorgsky's Coronation Scene from "Boris Godunov." If Bernstein conducts it, he cannot make the chorus shout "Lennie!"

This scene was the first of four excerpts from "Boris" presented last night by the National Symphony Orchestra -- the only moment of triumph in a series of episodes that deal mainly with anguished paranoia, remorse of conscience and death. The music opens with a bang and ends with a whimper: "Uspe'" ("He is dead"), barely breathed by the chorus after the flawed, tragic tsar has collapsed, muttering "Prostite . . . prostite" ("Forgive, forgive.")

Balancing the chorus, and fully a match for its 100-plus singers, was Finnish bass Matti Salminen, a mountain of a man with a voice of limitless depth, enormous richness, overwhelming power and subtlety. He is a singer born to sing Mussorgsky's doomed monarch, and he sang it with a style to equal the greatest interpreters in its history.

This was Rostropovich's first venture this season into the Russian repertoire that is usually considered his specialty. It was outstanding, and it earned a long standing ovation. But, remarkably, it was not significantly more impressive than the Beethoven, the Baroque music and the new American music Rostropovich has conducted in the last two weeks -- or the two Sibelius works that opened last night's program, the "Karelia" Overture and the spare, somber Symphony No. 4 in A Minor.

In his eighth season with the NSO, Rostropovich no longer sounds like a Russian conductor learning other repertoire. He has become a generalist with a Russian flair, but his styles range from Bach to new music.

His Sibelius showed a fine sense of the music's structures and emotional tensions, but above all a mastery of the sound textures that are the root of so much of its power. The Fourth Symphony opened with wonderful, dark sounds from the orchestra's bass section, quickly followed by a superb solo from principal cellist John Martin. Moments of brightness flickered and disappeared, like the fitful sunlight of a far northern winter, and the music faded slowly into a final, soft sigh of despair.

The Oratorio Society's fine diction, well-balanced tone and precise coordination contributed greatly to the two segments in which it sang. But the spotlight was on Salminen in all four selections, and he sang alone in two of the opera's greatest moments: the Clock Scene and the monologue, "Supreme power is mine." A tenor from the chorus, Starling Hatchett, supplied a few lines of dialogue. He did it with good grace, but it must be uncomfortable to be the only other solo voice sharing a stage with Salminen.

The orchestration used was that of Rimsky-Korsakov, more colorful than Mussorgsky's own but lacking some of the elemental power of the original. In the coronation scene, a recording of church bells was used -- the familiar one from the annual "1812" Overture performances, augmented with a loan from the Metropolitan Opera. In the first performance, this sound would have been more effective if the volume had been a bit higher.