The main problem with the late Beethoven quartets is one of scope. These works stretch the expressive potential of the string quartet to the limit. While they are conceived on a scale comparable to that of any of his major orchestral works, they face the tremendous problem of developing within the bounds of an idiom whose orchestrational possibilities are very limited. As a result, Beethoven sometimes demands more of the string quartet than can be done with the instruments at hand. His Quartet in A Minor, Op. 132, however, carefully skirts any such fault. Ideally played, it demonstrates true virtuoso quartet playing, combining a great technical difficulty with the exceedingly delicate job of transmitting to the audience a sense of the total structure of the piece.

The Guarneri String Quartet's performance of the work at Sanders Theater, in the fourth concert of its series here, was of virtuoso caliber. The most significant aspect of this performance was that the second movement, un poco adagio, posed no problems of continuity to the listener. Throughout, the Quartet played with freedom and sensitivity, and brought out fully the singing qualities of the music.

Leading up to it were two works, the Mozart Quintet in F Major, K. 168, and the Quartet No. 2 (1958), of Leon Kirchner. Whereas the Beethoven is obviously a tremendous intellectual challenge to performers, the Mozart is deceptively simple. The Guarneri Quartet, fortunately, was not deceived. The pitfall with this, as with many other Mozart works, is that the player or players will not make the most of the symmetry of the music, and will turn out aperformance that is drab and uninteresting. While one may argue that the music is overly simple, one must remember that this is a studied simplicity, consciously reduced to the essentials and devoid of pedantry and presumptuousness. Looked at in this light, it becomes clear that the Mozart is fully as great a compositional achievement as the Beethoven.

The Guarneri Quartet fully understood the interpretational problem involved, and played was a great awareness of the piece's total effectiveness. Only the somewhat staccato playing in the third movement could be questioned.

The Kirchner was somewhat disconcerting after the Mozart. This quartet bases its appeal on a thorough-going exploration of the tone-colors one can produce using four stringed instruments. Although the expressiveness of the work is unquestionable, its continuity, or more specificaly its organization in terms of building and climaxes, is often unclear. To be sure, the Quartet's handling of the music emphasized those places in which there was a definite sense of increasing tension followed by release. This was particularly evident in the first movement, and less so in the second and third. The overall performance was in every was satisfactory despite a mechanical flaw (a string broke) in David Soyer's cello.