Frivolities rather dominated the program Saturday nightin the Kennedy Center Concert Hall; the most substantial piece of music was Stravinsky's "Petrushka" Suite, and it was preceded by Respighi's "Roman Festivals," Paganini's First Violin Concerto and Sarasate's "Carmen" Fantasy.

It added little to what had been revealed the previous evening about guest conductor Hiroyuki Iwaki's conducting abilities, and I suppose it would hardly have been worth attending except that it was a delight from beginning to end.

Iwaki demonstrated even more conclusively in the Respighi and Stravinsky what he had clearly indicated the night before in Sibelius Second Symphony sound like a virtuoso orchestra. Neither piece offered substantial data on his ability to sustain a lengthy, subtly nuanced musical structure (Mahler, Bruckner or Brahms, for example), but that is hardly a matter to be settled ona summer evening after a relatively shore rehearsal time.

Violinist Azron Rosand was the soloist in the Paganini and Sarasate works, playing with spectacular technique and a tone that you could spread on pancakes. I thought he went microscopically off key once or twice, but if so the lapses were slight and fleeting. The orchestra's string section joined the audience in applauding him with almost unanimous enthusiasm.