A warm, vigorous and enormously appealing new trio for violin, cello and piano by the eminent American composer George Rochberg received its premiere last night at the Library of Congress, which commissioned it.

It was played by the Beaux Arts Trio, the library's resident trio, in a lovely concert at the Coolidge Auditorium that emphasized the lyric side of the trio repertory.

The boldest thing about the new four-movement Rochberg work is its unabashed romantic ardor. Such a work would have been unfashionable if it had appeared 25 years ago when much of music was bordering on incommunicative. But now the pendulum is swinging back.

The Rochberg first movement starts in an almost pastoral mood; there then follows a turbulent section, and then a debonair theme with almost a touch of 18th-century decorum about it. The marking is Amabile, and that's exactly how it turns out. Some of these melodies kept reminding me of late French Romanticism, though the modulations upon which they rest would have shocked the French Romantic ear. Textures throughout are lovely.

Oddly enough, the movement in which the notion of conflict is developed the most consistently is the slow movement. It is an arresting combination of a very straight and lovely lyric theme (none of those jarring modulations here) played consistently against dissonant material from other instruments, which keeps the theme from ever really settling down. It is first strings with the main theme against piano, then vice versa.

Rochberg's Trio is compact and beautifully crafted, and it has something to say. Pianist Menahem Pressler announced that the full, ardent performance would be dedicated to the memory of Donald Leavitt, the former chief of the library's Music Division, who died late last year.

The Beaux Arts also played that big, urgent Mendelssohn Trio, Op. 66; a lovely little Schubert Notturno in E-flat that sounded almost like a bel canto opera duet; and a Haydn Trio in E-flat, H. XV:10.