The last concert of the 40th American Music Festival performed by the National Gallery Orchestra last night at the National Gallery conjured two neatly symmetrical images in the listener's mind: The homogenization of diverse influences bubbling from the caldron of the American "melting pot," and, more intimately, a mental panorama of a musical landscape as abundant as the nation's physical topography.

Conductor Richard Bales ended the series with three works, two receiving first Washington performances--Dai-Keong Lee's Symphony No. 1, and John Knowles Paine's Symphony No. 2 in A. Paine's grandiose four-movement piece, subtitled "In Spring," was the more successful premiere, lending its programmatic connotation to the mood of the holiday weekend, the unofficial end of spring.

This home-grown pastoral, rooted in 19th-century Romanticism, nonetheless bore the indelible stamp of the composer's artistic signature. The ensemble sharply defined the symphony's brilliant orchestral color and soaring themes. It is a splendid work, given a joyfully pervasive interpretation and deserving of future performances.

Lee's first symphony, composed in 1947, is in three movements. Alternating textures, shifting sonorities, urgent tempi and repetitive brass or percussion punctuation marked the first and third movements; sandwiched between is the masterly written (and gorgeously played) Adante espressivo, providing contrast with its languorous development and mood. The lasting impression, however, is that Lee's work is reminiscent of a soundtrack for a motion picture spectacular, background music for a personal "Fantasia" of the mind, drawing as it does vivid mental images of conflict and resolution.

The program opened with Fugue from Symphony No. 4 by Charles Ives.