An Italian pianist little known in this country named Michele Campanella stepped in for an ailing Martha Argerich at last night's Philadelphia Orchestra concert and scored a triumph.

The work was Prokofiev's third concerto, that wonderful combination of the mordant and the lyric, the dissonant and the consonant, that has become one of today's most popular concertos (it was what the contestants were wrestling away at in the finals in the movie "The Competition").

I haven't heard anyone do more with it than Campanella and conductor Riccardo Muti did last night at the Kennedy Center. It is a virtuoso piece both for the soloist and the orchestra; the two are very tricky to mesh, and one often dominates at the expense of the other. Not with Campanella and Muti. Nothing seemed rushed, and everything unfolded clearly. Yet the atmosphere was quite electric. And the normally subdued Philadelphia Orchestra subscription audience rewarded Campanella with a chorus of cheers.

The Prokofiev came as part of a program devoted entirely to music of the 1920s.

Just as beautiful as the Prokofiev, and much more rare, was Stravinsky's rapt, dreamy work for string orchestra, "Apollon Musage te," a ballet in two scenes. "Apollon" is the neoclassical Stravinsky at its peak, a work so opposite in character from the barbarism of "Sacre du Printemps" that it's startling it could have come from the same pen.

"Apollon," first performed at the Library of Congress, sounds like a work tailor-made for the Philadelphia. So it is all the more amazing to read in the program a note to this effect: "first performance at these concerts." How could such a major work for strings not have been done before by the orchestra that many feel to have the finest string section in the world? What other string section could produce those huge chords that come near the end with such a combination of precision and delicacy?

Finally, there was Ravel's "Bolero" -- in a performance that practically shook the place.