The 47th season of Pan American Union concerts opened last night with a delightful program of fresh and graceful playing by the Saint Germain Quartet. Not the expected ensemble of strings, the Saint Germain group consists of flute, violin, cello and piano. The combination allows for exploration of less frequently traveled territory, which on this particular evening included engaging works by Hummel and Weber and a premiere by Charles Callahan.

Due to the illness of violinist Nancy Lederer, the quartet, which is based in New York, was reduced to a trio. Her absence necessitated only one change in the program -- the opening Handel quartet was replaced by a Handel sonata. Actually a flute sonata with piano and cello obbligato accompaniment, the work gave flutist Deborah Jean Nathan an opportunity to show off her buoyant style, which set the tone for the entire recital.

In their three years of playing together Nathan and cellist Ettie Minor and pianist Pauline Lederer have developed a warm exchange marked by a nicely refined sensitivity. Though Nathan's exuberance often dominates, Minor is clearly a thoughtful musician and Lederer a skilled chamber pianist. mThese talented players could easily intensify their impact by giving thought to more subtle inflection of line and greater rhythmic flexibility.

Composer Charles Callahan, a young Bostonian now living in Washington, contributed "Three Lyric Pieces," which were dedicated to Nathan. Highly influenced by the French style, these brief works proved quite pleasing in their gentle, confident lyricism.