On Saturday night, the 245th anniversary of the death of Antonio Stradivari, the Juilliard Quartet paid him the best of all tributes. It gave a memorial concert in the Library of Congress using four of his priceless instruments with a power, delicacy and virtuoso technique worthy of the superb quality built into them.

Stradivari built better than he knew. He would not have known what was meant by the words "string quartet." He hardly could have imagined any of the music on the memorial program, all of which was composed by men born after his death and in styles undreamed of during his lifetime. Nor could he have imagined four players of the caliber of the Juilliard members playing together. Except for the virtuoso who might come along once in a generation--a Biber or a Locatelli, perhaps -- stringed instruments were simply not played in the 17th and 18th centuries at the technical level that is taken for granted today.

But the Library's four Stradivari instruments and the hundreds of others made by him and his great Italian colleagues contained these developments in embryo, the way an oak is contained in an acorn. Advances in technique and new developments in composing styles became possible precisely because such great instruments were being built--instruments capable of more than had ever been tried.

This year's program was a fitting tribute: a high-energy performance of Boccherini's Quartet in A, Op. 33, No. 6, that did not lose delicacy or thoughtfulness in its virtuosity; a brilliant reading of Anton Webern's brief but ultravaried and highly expressive Five Movements, Op. 3; and an intense, pensive, ultimately joyful reading of Schubert's Quartet in G, D. 887. The entire quartet was in top form, particularly first violinist Robert Mann, who played with more spirit and precision than he had shown in a long time.