The Orpheus Chamber Ensemble, which specializes in neglected music, focused on the young Beethoven yesterday afternoon in the Masur Auditorium at the National Institutes of Health. In a nearly flawless program, which opened with his String Quintet in C, Op. 29, and concluded with his E-flat Septet, Op. 20, the group presented a brilliant, self-confident musician, clearly a master of the forms inherited from Mozart and Haydn but beginning to chafe at the restrictions of 18th-century style with an occasional radical modulation, a touch of brusqueness under the music's polished surface.

Between the two Beethoven pieces, the group performed Samuel Barber's delectable "Summer Music" for wind quintet, a jaunty celebration of the distinctive voices of flute, oboe, clarinet, bassoon and French horn, and the smooth textures they produce when playing together. The performances were totally beguiling -- straightforward in interpretation, well-paced and beautifully balanced, with a particular charm in the dialogues between strings and winds in the Beethoven Septet. Violinist Naoko Tanaka stood out in the frequent solos bestowed on her by Beethoven, and notable work was also done by clarinetist David Singer and Scott Temple, who made his French horn sound like an instrument created for chamber music.