Friday night at the Library of Congress was one of those occasions when the main event overshadowed all that went before it.

The main event was the Berg Concerto for solo violin, solo piano, and thirteen wind instruments. The soloists were Edith Peinemann and Walter Klien, who had, in the first half of the concert, tendered proper accounts of the C Minor Sonata by Beethoven and the seldom-heard Sonata in A Minor by Schumann. Peinemann has been enjoyed here in past seasons, and Klien is one of the admirable though lesser-known European pianists whom we have had too little opportunity to appreciate.

For the Berg Concerto, conductor Frederik Prausnitz led a Washington ensemble called the MusicCrafters, whose work in the demanding score was more than competent.

Berg delighted in planting cues in his Chamber Concerto: notes whose letters -- A, B, C, etc. -- are used to represent Schoenberg, Webern and Berg. The number three appears in myriad ways: Three movements use three sonorities, the piano, the violin, and the winds.

All these, however, were the composerhs own working affiar. Today the concerto stands as one of the challenges of Berg's great era, a challenge that is being more fully understood as we move somewhat out of that era. While the concerto profited from the expertise of Peinemann. Klien and Prausnitz, and was admirably played, there is a greater degree of lyric poetry in the music than was apparent much of the time. It is quite possible that if these same musicians were able to play the concerto over for another two or three months, they would find ways of disclosing its inner secrets more than they did on Friday.