Like everyone else, I wrote an appreciation of Mstislav Rostropovich recently. (The great cellist died on April 27.) And, like everyone else, I mentioned that he had not only been a great player but had also been a great teacher. Not all the great players can teach, as you well know. These are separate (if related) gifts: playing and teaching.

So it was with some curiosity that I went to a master class given by Yefim Bronfman at Mannes College last month. Mr. Bronfman is one of the top pianists of our time, and he is a top pianist for any time. But what would he have to say? Would he be able to impart any of what he knows — and what he senses, what he feels – to others?

Oh, yes. Mr. Bronfman did some of the best teaching you can ever hope to witness. I would go so far as to say it was revelatory. He taught in two pieces that are extremely well-known: Beethoven’s Piano Concerto in C minor and his “Moonlight” Sonata. Familiar as they are, you felt, when Mr. Bronfman was through, that you had hardly known them.

The first student played the Cminor concerto. After the student ended the first movement, Mr. Bronfman said, “Bravo. I liked it. It was never boring, and that’s a great achievement.” Then he commenced to teach. And, polite and encouraging as he was, he never hesitated to give a candid assessment or candid advice.

Moreover, that advice was good for everyone in the room — not just for the particular student, playing his particular piece. That is crucial in a master class. You are not teaching for the few onstage, you are teaching for the many in the audience.

One of the first things he told the concerto student was, “Your passagework is too Lisztian. It should be more Classical — at least, as I understand the piece.” Mr. Bronfman was always doing this: saying, “as I see it,” and “in my opinion,” and “for me.” He rarely said, “Do this, do that.” Instead, he would say, “I would do this, I would do that.”

But, frankly, most of what Mr. Bronfman had to say sounded more like absolute truth than personal opinion.

All through the master class, Mr. Bronfman did a combination of talking and demonstrating — that is, of using words and using the keyboard (letting his fingers do the talking). His command of English is excellent, even enviably so. He has a knack for choosing the right word: “These rests need to be more dramatic, more eventful.”

As he went through the C-minor concerto, he addressed every dynamic and every shading. And there are many of them, almost endless possibilities! But some possibilities are better than others. Mr. Bronfman proved this beyond a doubt.

And he was pretty quick with a quip, or an aphorism. He advised this student, “Sometimes less is more” — then added, “Sometimes less is less. Sometimes more is more.” It depends, and musical sense must guide you.

“When the orchestra plays this, you must react to it. You must be like an actor, responding to something he has heard. Don’t just go along.” A little later: “Play this passage as though commenting on what the orchestra has done” — the notes do not originate with the piano.

Over and over, he pointed out things that you had never noticed in the piece (or that I had never noticed, perhaps I should say): “You hear that? That’s a split-second dissonance.” Let’s not allow that to go by the way.

When the student used an excess of rubato, Mr. Bronfman said, “Why are you taking time there?” Then he told a story about Erich Leinsdorf. Once, when Mr. Bronfman was young, the famed conductor chided him for messing around in a Mozart concerto. Said Mr. Bronfman to the Mannes student, “Keep the big picture in mind.” In other words, think of the flow and structure of the entire piece, not just the phrase that happens to be enchanting you.

He also said, “Just because you’re in time does not mean you’re not free.” And, “If you want to be especially expressive here, do it with color” — not with rubato.

Speaking of colors: Mr. Bronfman pointed out that, on repeated notes, if you change your fingering, you change the coloring. A remarkable observation, or fact: The use of different fingers results in different tonal colors.

And Mr. Bronfman said many things that were quite unexpected, against the grain. For example, teachers often emphasize the unity of the hands: The right and left must work together. But Mr. Bronfman said, at a particular point, “Don’t let your right hand interfere with your left hand — they should be completely independent.”

He also said many things of considerable subtlety — things that make artistic sense, if not ordinary sense: “This should be impatient, yet at the same time settled.” And, in the “Moonlight” Sonata, “I would not make a crescendo there — not with volume. Let the change of harmony make your crescendo.” He was particularly good on the art of pedaling, an art that is frequently ignored, or unthought of. A sample: “Leave the pedal a little dirty here” — i.e., let the sounds, notes, and colors mix a little, blur a little.

And he was repeatedly pointing out the sheer unusualness of Beethoven’s music. Over and over, in both the concerto and the sonata, Mr. Bronfman said, “Beethoven could have written this” — and then he went on to play something conventional. “But instead he wrote this” — something unexpected, amazing. Moral: “That is a remarkable moment — you should take advantage of it.” Moreover, he constantly directed attention back to the score. Often, he was quite charming about this (but not consciously so): He would show the student the score, shrug his shoulders, and give an apologetic look — a look that said, “Hey, what can I do? Beethoven has written it. It’s not me, Yefim Bronfman, talking — it’s Beethoven.” His teaching underlined both the primacy of the composer’s — any composer’s — intentions and Beethoven’s particular genius.

And his playing, his demonstrating? Almost beyond praise. It is commonly said that, the worse the teacher, the more he demonstrates. But this is not necessarily so. Sometimes a quick demonstration is worth a thousand words — and it is definitely part of teaching. To hear Mr. Bronfman play, and talk, was a profound experience (as well as a dazzling one).

When the first Mannes student left the stage, Mr. Bronfman said, “Of course, you should feel free to disregard everything we’ve talked about.” I wouldn’t — and neither would anyone else.