One thing that sets Mstislav Rostropovich apart from many conductors is his awareness that he lives in the 20th century, as he demonstrated intensely Thursday night in the Kennedy Center Concert Hall. He conducted three substantial compositions from this century and only Beethoven's "Egmont" Overture to represent the rest of music's long history.

The National Symphony's audience obviously enjoyed the program. Composers Robert Parris and Andreas Makris, both Washingtonians, received long, enthusiastic applause. The Third Symphony of Jean Sibelius was played with controlled energy, lyric lilt, vivid, well-balanced color and an exciting final climax.

The Symphonic Variations of Robert Parris, commissioned by Rostropovich and receiving their first performance, have a healthy sense of the theatrical. The music begins with the stage darkened and an offstage saxophone playing a plaintive, unaccompanied theme, and the light increases as other instruments join in. The orchestration integrates itself effectively into the music's intriguing structures, which might be called variations on the idea of musical variation. The first movement is a set of double variations that keep melting into one another; the second, a fairly standard theme with seven variations; and the third, a highly imaginative excursion into variations on the first two. Parris says he was unaware of the structure emerging in his third movement until much of it was already on paper. He has a clever subconscious and should nourish it carefully.

"Chromatokinesis" by Andreas Makris (an NSO violinist) is an essay in color and movement, as the Greek roots of its name indicate, but its first section (devoted to "color") is rich in movement, while the second (focused on "movement") is hardly colorless.

The orchestra may have put special affection into this music of a colleague, but the whole program was unusually well played, except for the rather tentative opening of Beethoven's "Egmont" Overture, which probably did not have as much rehearsal as it needed.