Seiji Ozawa had a fine idea at the beginning of the Boston Symphony concert in the Kennedy Center on Saturday night when he opened the program with the Five Pieces by Anton Webern and then, without any announcement, conducted them a second time. The BSO, now celebrating its 100th anniversary, played the U.S. premiere of these pieces in 1926.

The point of Ozawa's unusual exercise is that these unique gems, which take barely five minutes to perform, are beautiful in themselves and the epitome of wholeness in miniature. Scored for chamber orchestra, they are exquisite studies in sounds sculpted out of fragile silences. Precisely because they can pass us by without our having time to become aware of them, Ozawa's decision to repeat them gave his listeners, some of whom were confused by the process, the invaluable aid of hearing unfamiliar music twice. The musicians played with radiant beauty under inspired conducting.

Schubert's Unfinished Symphony, the utmost in familiarity, followed in a lovely relaxed but vital reading.

Richard Strauss' great tone poem, "Also sprach Zarathustra," stands at the opposite end of the universe from Webern's pieces. Indeed Webern was reacting against musical giantism in creating his filigreed brevities. "Zarathustra," too, has its place in the history of Bostonian greatness, for it was Serge Koussevitzky who showed the world certain ways of conducting the monumental work that no other conductor has matched.

Ozawa's reading was, relatively, a disappointment. The famous opening was insufficiently spacious, the organ repressed, and the trombones not given the breadth of phrasing that makes for the largest effect. The central portions of the work were beautifully played except for Ozawa's tendency to rush. Joseph Silverstein's magisterial violin playing typified the caliber of all the soloists, and the final page was truly moving.