Bernard Greenhouse pours out a cello tone as rich and creamy as chocolate mousse, while Isidore Cohen touches his A string with just the right amount of tremolo. Menahem Pressler (darting anxious glances around to be sure his partners are with him) moderates his piano tone from rolling thunder to the merest whisper. It is almost enough to convince you, for a minute or two, that Tchaikovsky's Trio in A minor is great music.

In fact, it is--for a minute or two, perhaps even a dozen--when the Beaux Arts Trio is playing it. The trouble is that it lasts quite a bit longer. Sometimes it sounds like a concerto without orchestra, substituting a series of solos for the dialogue that is the soul of chamber music. Sometimes it sounds like a song without words, offering pretty melody and empty rhetorical gestures instead of sequential logic.

And sometimes it is magnificent--notably in the variations movement (whose episodic form tends to mask Tchaikovsky's structural weaknesses) and particularly in the final coda, where the composer's grief expresses itself quietly and effectively, without the hysteria that was apt to creep in when Tchaikovsky had an orchestra at his disposal. This trio deserves a place in the repertoire for its best moments, and the Beaux Arts Trio states its case most eloquently.

Long familiar at the Library of Congress, the ensemble took a new role last night, as a group in residence sponsored by the recently established William and Adeline Croft Fund. The performance justified this new honor. Outside of a slightly ragged beginning in Haydn's Trio No. 15 in G, and one or two violin notes that were not quite dead center, there were few technical flaws. Superbly balanced throughout, the interpretation seemed particularly fine in the subtly shifting balances of Mendelssohn's Trio in D minor, the feathery lightness of its scherzo, the fine contrast between brilliance and schmaltz in its finale.