Katz has recovered from those severe health problems, including a ruptured disc caused by a fall. For many years, a progressive eye disease changed the shape of his corneas, dimming and distorting the marks he saw on the printed page. He lost his driver’s license and wore rigid contact lenses to maintain enough vision to function. A wise doctor urged him to put off surgery as long as possible, to wait for medical breakthroughs. To read sheet music, before the days of multifunction photocopiers, Katz had the pages enlarged by professional photo services. Using a home aquarium light, he rigged up a fluorescent lamp that he clamped on his stand and packed around the world during tours with the Cleveland Quartet. Then, in 1975 and 1977, corneal transplants permanently restored his vision.

“I’ve had career-threatening experiences,” he says, “so I empathize with students who are scared about physical problems. That’s why I teach how to play with healthy habits.”

As he attends to posture, left-hand angles, and bow-arm motions, he also nourishes the imaginations of his students.

Two of his former students, Jonathan Pegis and Brant Taylor, who now play in the Chicago Symphony Orchestra, remember getting their hands organized during the first year of study and then working to communicate musically.

“I never knew what he’d say when I finished playing,” says Taylor. “It might be something I’d never thought of in my life. He’d stare at the ceiling beyond me and squint his eyes, imagining a sound. Then he would move his hand to imitate fast, agile motions with the bow, showing me different ways to excite the string.”

Katz also knows how to use surprise and humor. He shocked students one April evening during a master class many years ago at Eastman. Pegis, his teaching assistant at the time, was about to play the Kodaly unaccompanied sonata.

As the two met in the hall before the class, Katz suggested they do something a little different. Pegis agreed. The students filed in, and Pegis sat down to perform the entire sonata from memory. When he finished, the students applauded.

Katz did not. Instead, he exploded.

“I am so ticked off!” he yelled at Pegis. “You aren’t doing any of the things we talked about in your lesson!”

The students couldn’t believe what they were seeing or hearing. Their jaws dropped with astonishment. Katz proceeded to criticize his assistant’s technique and to mock his musical interpretation, generally ripping him apart. Pegis looked more and more dejected, but he was trying not to laugh.

At last, Katz said, “Which of us is the better actor?”

Pegis grinned.

“April fool,” teacher and student said.