There may be a tight squeeze in Sanders Theatre on Monday, when the Guarneri String Quartet makes its final appearance at Harvard this summer. Certainly nearly everyone who was at this week's performance will be back to hear Arnold Steinhardt, John Dalley, Michael Tree, and David Soyer play more music from the-string quartet repertoire. Monday's concert--Schumann's Quartet in F Major, Op. 41, No. 2, Bartok's Quartet No. 5, and and Beethoven's Quartet in F Major, Op. 135, was a display of vitality, balance, and sensitivity.

The Schumann, which opened the program, has difficult passages for rhythmic ensemble and intonetion. But the quartet maintained excellent balance and infused the work with a vital spirit that is rarely heard. Even the third movement, which has some rather un-string quartetish passages, worked well in their hands.

The Bartok was something of a disappointment, not, it should be stressed, because of the performers, but rather because of a lack of direction in the piece itself. Each of the first four movements wanders somewhat aimlessly before it begins to build toward a climax. But when the tension is finally built up, just begging for resolution and conclusion, Bartok lets it crumble, making a long-winded, rambling apology instead. The finale, in contrast to the rest of the quartet, is a cohesive movement with direction, vitality, and a good share of tongue-in-cheek humor.

Certainly Beethoven's Op. 135 was the highlight of the evening. At the end of the fourth movement, a tremendous collective sigh echoed through Sanders. And one of those rare moments of complete audience involvement was reached at the climax of the second movement, when the intensity and sheer magnitude of the sound emanating from those four instruments was unbelievable.

But they played with more than just the skill and clarity and garce of four fine artists: they were a quartet from the first note to the last. It is this subordination of individual tendencies to the ensemble that makes the Guarneri String Quartet the rare group that it is.