The world premiere of a flute concerto by John LaMontaine was the centerpiece of the second concert in the National Gallery's 38th Annual American Festival yesterday.

Richard Bales conducted the new work with Keith Bryan as soloist. LaMontaine clearly had a great time writing the concerto, since he has filled it with wit and open, songful beauty. The formal design is neatly broken up into imaginative divisions. There are some exotic touches for woodblocks and bass clarinet, but the heart of the work lies in the brilliance of the writing for the soloist. Bryan carried off the premiere with great spirit, taking obvious pleasure in the virtuosity of the writing. The cadenza in the final movement is impressively introduced and beautifully concluded.

Bales and the orchestra handled the subtleties in the ensemble writing with a fine feeling for the balance between the soloist and the substantial support.

The evening began with Festivals for Orchestra by Richard Faith, music that kept sounding both Oriental and faintly like Puccini. Thomas Beveridge's spare Dialogues followed. After intermission there was an inconclusive Adagio by Nancy Van de Vate, and then the solid pleasures of a Sinfonitta by George Whitefield Chadwick. Bales dispatched the varied styles of the program with easy command.