The stage must be set before the master appears. On a Saturday afternoon in Bloomington, Indiana, a teaching assistant rolls the grand piano to the middle of the studio, scoots a pair of padded stools into place, and rests the master’s cello by its scroll on a chair in the front row, second from the end. Tradition reserves the first chair in the front row for the master himself. Audience seats are filling fast with local musicians and visitors from Europe. The first two students are getting ready to play: Chih-Hui Chan tunes her cello while Ayako Toba warms up at the keyboard. Tension fills the room. No one talks.

At 12:30 sharp, Janos Starker walks through the door. Looking professorial in a well-worn sport coat, he cracks a joke about the studio’s air conditioning. A curt nod and a wry smile to the audience are the only introduction he offers. The legendary cellist and teacher has arrived to preside over his weekly master class at Indiana University, where he has taught for 48 years.

At age 82, his face is softer than the severe visage that intimidated me when I played in his master class 30 years ago. His hair, now gray, still frames the endlessly high forehead that has distinguished his appearance since he was in his 20s. The demonic look of his youth may be gone, but he still radiates keen intelligence and steely confidence.

Seated, he arches an eyebrow. Chan takes the cue, nods to Toba, and they launch into the first movement of Schubert’s Arpeggione Sonata. Starker listens without interrupting. His lower lip pouts with concentration. His legs cross, and an arm drapes over the back of his cello’s chair. He gazes at the floor and, occasionally, glances at the performers. No expression reveals his opinion.

I remember sitting before him during a master class at the Aspen Music School in the 1970s. “Let me hear your power!” he commanded, boring into me with fiery, brown eyes. He watched me make a huge circle with my bow arm, then land on the open D string with a fortissimo down-bow. I was supposed to think “round” and remove any angles from my shoulder, elbow, wrist and fingers. His intense focus made it the down-bow I never forgot.

Now he turns his intensity on Chan. After a dramatic pause, he declares, “That could have been a performance. Beautiful playing.” Chan beams, and the whole room relaxes.

“But there are a few things we could discuss. An-tic-i-pa-tion,” he says slowly, exercising his smile muscles as he picks up his cello and bow. “Prepare your bow speed mentally, before you touch the string, like this. And do you hear that hairpin at the end of certain notes? Get rid of it.”

He works through the movement on his cello, exaggerating things he wants her to change. A short figure could sound “more Vienna.” The long, downward slide she played “went out in the 19th century.” During a turn, she accented the wrong note. No detail is too small to escape his notice or merit his attention. Yet no principle is too big to address, even for an advanced player.

“If you need more bows, take them. If the fourth finger doesn’t feel quite safe, use the third. And when you play, I see you move only to the left. Sometimes, you should move to the right. Balance.”

Things don’t go so well for the next player. When Haeyoon Shin finishes the second and third movements of the same sonata, Starker pronounces his judgment sternly: “You are halfway.”

Some of her shifts fell short of their targets in the upper registers. “Every single time, you are missing these shifts because they are not anticipated. Didn’t we talk about anticipated and delayed shifts?”

He shows her again how to move the left arm and deliver the finger on pitch.

“I said you should listen to some Schubert songs, and did you?” She silently shakes her head and looks at the floor. She has not listened. “It doesn’t go dy-a, dy-a, dy-a, like the maid singing in the kitchen!”

He plays the opening of the slow movement, articulating the grace notes in the cello’s fourth measure as if each were a syllable to be sung, then takes up at bar 35 playing the bass-register melody like the song of a stern father.

“There are three different characters of sound, three different personalities singing,” he tells her.

“Each must be expressed.”

Starker has reached the highest levels of music making from a humble beginning. Born in Budapest, Hungary, in 1924, the son of a Polish tailor and a Ukrainian mother, he had no official citizenship until 1954, when he became a citizen of the United States. His two older brothers began violin lessons at an early age, and Janos took up the cello at age six. His only teacher was Adolf Schiffer, a bookkeeper who taught himself the cello well enough to enter the class of the illustrious David Popper and to succeed him as professor at the Franz Liszt Academy of Music. Starker never graduated from high school, because he left at age 15 to play professionally and to study the humanities privately with a university professor.

During World War II, his family suffered persecution as Jews. Starker’s older brothers were marched to Yugoslavia in 1944, where Starker believes they were shot by Nazi soldiers. Janos spent several months in a Nazi work camp, but was freed due to the intervention of a Swedish couple, friends of his esteemed cello teacher Schiffer.