Last night's National Symphony Orchestra concert was a tribute to Mr. and Mrs. Lee D. Butler, in appreciation of their 50 years' support.

Mstislav Rostropovich opened the concert with the early Divertimento for strings by Mozart, K. 138. Using a larger ensemble than might have been expected, Rostropovich elicited playing of utmost delicacy in the andante, and fine, robust tone in the outer sections.

For the Fifth Brandenburg Concerto of Bach, he reduced the orchestra to 14 plus three soloists: Miran Kojian, violin; Toshiko Kohno, flute; and Anthony Newman, harpsichord. The spirit of the work was strong in the vital outer rhythms and intimate interplay of solo voices in the slow episode where Newman provided ideal realization, and Kohno and Kojian proved a model team. Had Newman made the cadenza at the end of the first movement something more flexible and personal, his playing would have been admirable.

The evening closed with Harold in Italy by Berlioz with the notable solo voices of Dotian Carter on the harp, and, gleaming in the stage lights, the sound of the very Stradivarius viola once owned by Paganini that inspired the music, played by Richard Parnas.

Parnas played handsomely, but it is impossible to hear Harold without realizing how often Berlioz covered the viola with other instruments. Rostropovich held the work together well and made the most of its closing orgy.