Thursday night at the Library of Congress the Juilliard String Quartet interrupted its sequence of Beethoven programs to play some Haydn, Schumann and Schubert. Appropriately, considering that we are in the midst of his 250th birthday celebration, the juxtapositions of the program made clear the creative explosion Haydn set off in the string quartet form.

The Juilliard chose to open with Haydn's E-flat Major Quartet, Op. 76, No. 6, not the most admired of the Op. 76 set or of his quartets in general. However, the choice proved inspired. The work is a storehouse of seminal ideas that point to future possibilities in a way not as obvious in some of his more complete statements.

The rich texture of the following Schumann A-Minor Quartet, Op. 41, No. 1, came as a logical extension of the frequent linear complexity of the Haydn exchanges. It seemed as if Schumann was merely adding another chapter to the same book, which, in a broad sense, he was.

And the exquisite cello lines of Schubert's C-Major Quintet, along with the hymnlike second movement, sounded like an inspired expansion of what were no more than hints dropped earlier by Haydn.

During the first half of the program the Juilliard sometimes played with more spirit than accuracy. In particular, first violinist Robert Mann did not always seem to be right in the center of the pitch.

Joining the ensemble for the Schubert Quintet in the second half, cellist Bernard Greenhouse inspired both more precision and more subtlety. His exchanges with cellist Joel Krosnick, especially in the first movement, possessed an exquisite delicacy. Though the other Juilliard members echoed Greenhouse's spacious approach, violinist Mann maintained an insistent intensity that occasionally bordered on the strident.