In his "Black Dance," which pianist Caio Pagano played as his first encore last night at the Library of Congress, Brazilian composer Camargo Guarnieri sounds like a tropical Gershwin, even richer in his harmonies and more vigorous in his rhythms.

In Sonatina VI, the last piece on the program, Guarnieri is a cosmopolitan composer who writes charming atonal melodies and manipulates counterpoint like a master--endowing it with a special excitement and bringing its interactions to a shattering climax. The Sonatina was composed for Pagano, who plays it with overwhelming effect.

Last night's concert was sponsored by the Hispanic Division of the Library of Congress, in cooperation with the Brazilian Embassy and the Brazilian-American Cultural Institute, as part of a multimedia program commemorating the Week of Modern Art in Sao Paolo in 1922, an event that revolutionized Brazilian awareness of modern art much as the Armory Show did in this country. Pagano began by repeating and enlarging a program of Villa-Lobos and Debussy originally performed by the great Guiomar Novaes in 1922. He played with a fine sense of style and flawless technique. After intermission, he added music from contemporary Brazil--a sampling of the long-term results of the revolution in taste that began in 1922.

Besides the Guarnieri piece, the program included "Cartas Celestes Star Maps III" by Jose' de Almeida Prado, a brilliant pianistic piece of program music that portrays the moon in all four of its quarters as a recurring motif, tying together such portraits as "Orion, the Hunter," galloping in hot pursuit of prey, Taurus, bellowing like a bull, and "Mars, the War God," marching ominously through scenes of destruction while the piano makes sounds uncannily like a drum. This, too, was dedicated to Pagano and provides music to match his superb technique.