The Audubon String Quartet, a brilliant young ensemble that is in residence at Virginia Polytechnic Institute, suffered a major injury last week: second violinist Sharon Smith Polifrone broke the middle finger of her left hand. Even with a fine substitute for yesterday's program at the Wolf Trap Barns--Janet Brady, former second violinist for the ensemble--it was understandable that the players sounded somewhat tentative in the opening bars of Mozart's Quartet in D minor, K. 421, and that the viola and cello seemed more at ease than the violins throughout the program.

Even with these problems, however, this was a beautiful program, beautifully played and greatly enhanced by its surroundings: a concert hall as finely tuned as an old violin. The wood, older than most of the music being performed, enriches the tone of any instrument but particularly of a string quartet.

Following Mozart on the program and performed with even more charm were the vigorous, tuneful Quartet No. 17 of Heitor Villa-Lobos and Dvorak's splendidly melodic "American" Quartet in F. Cellist Thomas Shaw and violist Doris Lederer Horwitz were particularly eloquent in the Dvorak. The enthusiastic audience seemed very small, even in this tiny hall. It may take a while for the music lovers of Northern Virginia to discover that Wolf Trap is now a small winter place as well as a large summer place, but the quality of what is being done there should speed the process.