In last night's program at the Library of Congress (to be repeated and broadcast live tonight on WETA-FM 91 at 8), the Juilliard Quartet completed the Beethoven cycle that it began last spring. Some of the best music in the cycle was saved for last, including the final Quartet in F, Op. 135, where Beethoven comes to terms with his approaching death; the magnificent transitional Quartet in F minor, Op. 95, in which the great composer begins to develop the transcendent style of his late quartets, and the sixth and most interesting work of the Op. 18 set, whose last movement, titled "Melancholy," looks ahead (albeit rather palely) to the subject-matter and style of Beethoven's last years.

In all of these works, the performance was fully worthy of the music and of the Juilliard's reputation. A few intonation problems were inconsequential last night but may seem more important in the live recording planned for release by CBS. As nearly always happens, the Juilliard's natural style had a bit more weight and energy than feels comfortable in the early Op. 18 quartets. But No. 6 seems to be an exception; it is more hospitable to the Juilliard manner and, in turn, the players seemed to adapt their approach to the music's needs. They leapt joyfully into the light, bouncy melody that opens this work, perhaps because they were anticipating the moody, quirky music that follows.

As for the later works, their energy, profundity and subtlety of dialogue are as natural to this ensemble as breathing. The music is greater than any possible performance, but a substantial part of its greatness was explored last night.

Also on the program were two works that had to be included to make the cycle complete: Op. 18 No. 3 in D and the second finale Beethoven composed for his Op. 130 Quartet because the original last movement, the Grosse Fuge, was considered too long by Beethoven's publisher. The Op. 130 segment was played as a sort of encore, with a fine lilt and e'lan. Op. 18 No. 3 did not sound nearly as interesting as No. 6 -- perhaps because, in fact, it isn't.