The matchless Beaux Arts Trio inaugurated its month-long survey of Beethoven's piano trios at the Library of Congress last night with Bar One, literally. It was the great man's Opus 1, Number 1 -- the Trio in E-flat major, from 1794-1795.

No one pretends that it was in any way Beethoven's first work. No composer had his eye on posterity more intently from the beginning than Beethoven, and he must have agonized over what would occupy the initial position in his musical legacy. That selection may have had more trial runs than Wendy's before they came up with "Where's the beef?"

The piece was a worthy choice. It is written within a Haydnesque framework, but there are traces of the Beethoven to come -- plunges with dramatic abruptness into moods that Haydn would not have leapt to. Yet, there is little hint of the composer who eight years later would inalterably change the course of musical history with the scale of the "Eroica" symphony.

And there was no trace of this Beethoven in last night's concert until the somber, poignant slow movement of the "Ghost" trio, written six years after the "Eroica." That was a Beethoven riding the cutting edge of musical adventure, a course to which he would remain committed for the subsequent two decades of his life.

No group, really, plays this material better then Isidore Cohen, Bernard Greenhouse and Menahem Pressler. These works are the very heart of the trio repertory -- especially the "Archduke" trio, which will conclude this series in three weeks. The Beaux Arts Trio has played, and recorded, these works so often that things seem second nature, but there is no suggestion of settling into a routine. In fact, one does not recall hearing them in finer, and fresher, form than last night. The music -- including the B-flat trio, Op. 11 and the posthumous E-flat -- positively glowed. Attacks, releases and dovetailing of phrases were both precise and seemingly effortless.

It was a model of what is unique about chamber music.