Mstislav Rostropovich opened his seventh season as music director of the National Symphony Orchestra last night with a great anthem of struggle and triumph: the Second Symphony of Jan Sibelius--an appropriate work for an orchestra that is reaching new artistic heights in an atmosphere of financial struggle.

The symphony has not previously been part of his standard repertoire, but Rostropovich claimed it decisively as his own, much as he did last season with the music of Ralph Vaughan Williams.

The Sibelius Second is large in scale, rich in color and intense in feeling. If Rostropovich is not yet fully habituated to this score, his interpretation showed the results of careful study as well as a natural affinity. Some passages will benefit from further polishing in later performances, notably the slightly square phrasing of the opening bars in the first movement. But there was a power, an excitement and a vitality in this interpretation that swept small reservations into oblivion.

Rostropovich's interpretation is highly individual, though essentially in the mainstream of the work's performance tradition. It is probably not fanciful to see his performance as a personal tribute to Serge Koussevitzky, one of his prime inspirations as a conductor and the man who for a generation was most closely identified with the work. It will be a while before Rostropovich and the NSO achieve the polished mastery that Koussevitzky and the Boston Symphony reached in this work after they had been together for a quarter century. But the potential is clearly there.

Moments of grandeur abounded, and the interpretation was on a very high level from the first great crescendo in the first movement to the final climax. One might have wished for even more brass power at the end, but the climax was nonetheless shattering--and there are always grounds to wish for more brass at this point. Perhaps the most impressive section in an interpretation that had many was the deep bass opening of the second movement, beautifully phrased and controlled, with exquisite balance between the texture of low winds and plucked strings.

Besides the Sibelius--the major event of the evening--the program included a bright, brisk interpretation of Elliott Carter's powerful, buoyant and melodious "Holiday" Overture--a winning, rather Copland-esque work by a young composer who now, in his 75th year, has acquired a reputation for rather cerebral, complex music. Rostropovich's high-energy interpretation made the most of the music's attraction.

Wagner's Wesendonk Lieder were sung by mezzo soprano Glenda Maurice with a wonderfully rich, warm lower register, precise diction and a wide range of emotional expression. In this music, as he has done many times before, Rostropovich showed himself an unsually fine vocal accompanist, supporting the voice as exquisitely as he does when his wife, soprano Galina Vishnevskaya, is the singer. If he ever finds the time, amid all his other commitments, it would be good to hear him doing more work with operatic material.

Last night's performance was given under a special handicap; an electrical fire in the Kennedy Center knocked out several transformers, making it impossible to provide air conditioning for the audience, many of whom were in black tie for an after-concert party to celebrate the opening of the season. But any discomfort was quickly forgotten as the music took control of the audience.