This year at the Salzburg Festival, there are 195 performances. The one I was looking forward to the most was a recital by Krassimira Stoyanova, the Bulgarian soprano. She is a great, and touching, and versatile singer. I have heard her in operas by Mozart, Verdi, and Strauss. I have heard her in Beethoven’s Ninth and other such works.

Hang on: there are no other such works.

Anyway, I had never heard Stoyanova in recital. And, on Friday night, she appeared in the Great Hall of the Mozarteum, accompanied by a German pianist, Jendrik Springer. The first half of their recital was German: Berg and Strauss. The second half was Russian: Tchaikovsky and Rachmaninoff.

I will make a few general remarks about Stoyanova and her singing. She is warm, gracious, intelligent, musical, interesting, and beautiful—beautiful in every way you can count. “You play who you are,” goes an old saying in music. You also sing who you are. From Stoyanova, a goodness emerges. You hear the same in Heidi Grant Murphy, to name another soprano.

Speaking of sopranos: I did a public interview the other week with Golda Schultz, the young South African. Two of her favorite singers today, she said, are Stoyanova and Anja Harteros. And they have this in common, she noted: they both sing like instrumentalists.

That’s an interesting point.

Richard Strauss loved the soprano voice, and he would have loved Stoyanova. She loves him back. Stoyanova is a natural for Strauss, like Jessye Norman, for example. “I like my songs best,” said Strauss (to Hans Hotter, the bass-baritone). What he meant was, of all the music he had written, he liked his songs the best. I agree with him.

I have to tell you something funny about Stoyanova. Earlier, I mentioned her warmth, her outstanding warmth. Well, Strauss ends a song with the words “Mein Herz ist kalt”—“My heart is cold.” And, man, did Stoyanova sing it warmly. But you can make an interpretive argument!

Another song on the program was Strauss’s “Ich schwebe wie auf Engelsschwingen”—“I float as if on angels’ wings.” That is essentially what Stoyanova did in this song. She was light, high, and angelic.

Positioning herself for a high note—especially a difficult one—Stoyanova sort of tilts her head back. I thought of Dorothy Hamill and other figure skaters, beginning a layback spin.

I have gone too long without discussing the pianist, Mr. Springer, and I will say just a brief word. Throughout the evening, he was never less than adequate; and he was often quite good.

If you wanted to fault Stoyanova for something in the first half of her recital, you could say this: she was a little polite, a little “tasteful.” She did not plumb the depths, you could say. I would not argue with you, necessarily, except to say this: she knows that depths exist in the songs already; you don’t need to do much plumbing.

Regardless, she sang the second half of her recital—the Russian half, the Tchaikovsky and Rachmaninoff half—stunningly. She sang with extraordinary freedom, vocal and mental. She was full of passion, like the songs themselves. And she sang with extraordinary beauty. She was totally in her groove.

As she sang her Tchaikovsky group, I could not help thinking of her late countrywoman, the Bulgarian soprano Ghena Dimitrova—a great singer of Tchaikovsky.

Has Stoyanova recorded Tchaikovsky and Rachmaninoff songs? Googling tells me she has not, and that she has recorded precious few songs (as opposed to opera). What a pity. Maybe someone had a machine going on Friday night. It would be a service.

At the end of the evening, something strange and sorrowful happened. Stoyanova finished her Rachmaninoff group, having sung her heart out, and having sung magnificently. And a man (probably) in the balcony emitted a long, terrible boo. Stoyanova seemed startled. Then she looked up at the man and, with exaggerated and rebukeful formality, curtsied directly to him.

It was a nifty gesture. But I think I could see that the joy and satisfaction had drained from Stoyanova’s face. I think I could see that she was deflated: to face that boo after that recital.

She came out for many, many curtain calls before deigning to sing an encore. I believe she didn’t want to. I believe she was deflated, and soured. At last she sang something, which I’m afraid I can’t identify for you: it was possibly a Bulgarian lullaby.

The crowd asked for more, but she did not give it to them.

What did one boo matter, when the rest of the auditorium was cheering heartily? It matters a lot—and reminds me of a story.

This story was related to me by Ed Koch, who had a long tenure as mayor of New York. One day, he was riding in a limo with President Reagan. People were hailing and cheering the president. Suddenly, Reagan said, “Hey, did you see that guy give me the finger?” Koch said, “Mr. President, all of these people are expressing their enthusiasm for you, and you care about a guy with a finger?” Reagan responded, “That’s what Nancy says: I always see the guy with the finger.”

One does.