Antonio Stradivari died 248 years ago yesterday, but his instruments sound as though they may go on living forever. Last night in the Library of Congress' Coolidge Auditorium, the Juilliard String Quartet used them in four masterpieces, and the centuries-old violins, viola and cello took on a vitality, an incisiveness, a tenderness and an agility that are the hallmarks of youth.

One wonders whether string quartets will still be performing in public on the instrument maker's 500th anniversary, whether there will still be libraries and whether audiences will still gather, sit quietly in straight rows of chairs and clap their hands together when the music ends to show their enthusiasm.

But hearing those instruments at last night's memorial concert, it is hard to imagine that Stradivari's creations will not still be making music centuries from now -- perhaps music as unimaginable to us as the Brahms Sonata in D Minor, Op. 108, or the Dvora'k Piano Quartet in E-flat, Op. 87, would have been to the Baroque ears of Stradivari.

The Brahms was probably the finest performance in an evening in which the musical excitement was virtually nonstop. It was played by second violinist Earl Carlyss (who is soon to leave the Juilliard Quartet and take a position at the Peabody Conservatory), with guest artist Rudolf Firkusny engaging in a superbly coordinated dialogue from the piano. The performance was dazzling throughout -- most impressive, perhaps, in the slow movement, made memorable by the violinist's lyric warmth, the smooth execution of his double-stops.

The Dvora'k piano quartet was tense, colorful, full of tricky, well-executed rhythms. When cellist Joel Krosnick played his big melody at the beginning of the slow movement, the music stood poised tantalizingly on the brink of pure schmaltz without ever stepping over the line -- precisely as it should. Mozart's Piano Quartet in G Minor, K. 478, had an energy level that is not wholly approved for this composer and a style that gleefully sacrificed polish for impact. With the Juilliard and Firkusny, this worked well.

The evening opened with the slow third movement of Beethoven's Quartet in F Major, Op. 135, played as a tribute to the late Donald Leavitt, the chief of the music division of the Library of Congress until a few months ago. This music sounded like a prayer, mingling hope and sorrow in its chorale-like harmonies -- and that, too, was exactly right.