In January 1946, British impresario Walter Legge arrived in bomb-shattered Vienna in pursuit of musical talent. One of his discoveries, a young conductor named Herbert von Karajan, led him to another, soprano Elisabeth Schwarzkopf, who, said Karajan, "is potentially the best singer in Central Europe."

Within a few years two additional things had occurred. Schwarzkopf was developing into an even more important singer than Karajan had predicted, and she married Walter Legge.

Now, 36 years after that meeting in Vienna, the legendary Schwarzkopf is visiting Washington. Yesterday she gave a master class for young singers at American University. Afterward, she reflected on the art of singing and on the life she and Legge lived, during an interview at the residence of the head of the European Community, where she is a guest.

Legge and Schwarzkopf were one of the most famous and most gossiped about couples in music. Some rivals labeled Schwarzkopf "Her Master's Voice," a pun on the trademark of Legge's record company. Legge may not quite have been "the most influential man in 20th-century classical music," as alleged on the jacket of Schwarzkopf's new book, "On and Off the Record: A Memoir of Walter Legge." But he was the dominant figure in deciding which West European artists would record during the postwar period. Aside from Schwarzkopf, it was Legge, for instance, who brought us Maria Callas, Sir Thomas Beecham, Otto Klemperer, Artur Schnabel and Karajan (who wrote the book's introduction).

Schwarzkopf has been retired from the stage for six years and Legge died several years ago. But the fruits of their labors, it is now clear, are hardly exhausted. They had two of the finest musical and literary minds in the business, and it is Schwarzkopf's job now to preserve as much of this as possible.

At 66, she retains much of her fair-haired, blue-eyed, perfect-features beauty, and she seems full of drive for her new undertaking. The current book is based on Legge's papers, as annotated by Schwarzkopf. The next memoir will be her own, she said, and her conversation suggested some of its potential fascinations.

At the master class she had asked, "You know Callas?" to a young soprano singing Violetta's "Sempre libera." She was asked why she referred to Callas. "It is because you cannot any longer count on a young singer's having heard anything. The teachers don't teach them to listen. It is criminal. And Callas, well, a very major force she was." It is clear from the book that Callas returned the compliment, though sometimes in a characteristically tactless way.

Since Legge was Callas' producer, the subject of Callas' vocal problems in her later years was raised. "Well, you see," said Schwarzkopf, "there really has been a misconception about that. Those usual things they mention like Callas' weight loss were not her undoing. The problem that caused the wobble in her voice was something else, something surprising--it was about two years of clogged-up sinuses that she endured while continuing to sing. The common word for it is 'nasal drip.' "

Schwarzkopf was still in glorious voice at the same age at which Callas quit and she was asked if Callas' high bel canto voice might have been more vulnerable to strain than her own full, rich sound.

"In one sense, I think so," she replied. "On a regular basis she had to sing top C's, top D's and top E's quite regularly. And that is rather cruel to any voice. When I had a problem with a particular song, I could simply substitute one that worked better. But Callas couldn't do that."

Then, by way of contrast, Schwarzkopf mentioned her own "growing old of the voice process," which led to her retirement in 1976. "For me it was an interference with the hearing. I got to the point I could not hear myself in order to control the voice as I should."

A session yesterday with baritone Donald Culloff seemed typical of the psychology of her master classes. She confronted the student first and then started throwing challenges; in the case of the baritone's selection of Wolf songs it was in music closely identified with Schwarzkopf's own career.

Five notes into Wolf's "Fussreise" Schwarzkopf interrupted: "I heard you yesterday and I thought I would say before we lose time that you are very lazy about the upper voice."

A minute later, to the accompanist as well: "The two of you are both fortissimo. You ought to be pianissimo." They tried again.

But after a break of a few minutes, the baritone, who by then seemed fairly rattled, began another Wolf song, "Verborgenheit," and after a minute or two Schwarzkopf interrupted with a different kind of comment: "That is very beautiful already. And the voice sounds like a real baritone."

By the end, the most famous of modern-day Wolf singers was quite pleased with the young man, and when she led the applause, proud tears appeared in his eyes.

How can you be sure such a performer was not just having a bad day, Schwarzkopf was asked. "You can hear a bad day by experience," she answered. "Maybe this kind of teaching is cruel. But to be good, singers have to withstand a lot. I have yet to see one wilt in all the classes I have given. I think they realize I am on their side."

Schwarzkopf's answers to these questions had been so direct that she was asked something that singers almost always evade, "What is it that divides the superior singer from the great singer, that makes it possible to be careful about restrictions like meter, pulse and text while the voice still appears to flow freely?"

She did not evade. "I have been thinking about that, and I think I know. It goes back to one's vocal upbringing, where you learn to listen, as so many don't. You learn to sing not only with your own voice, but with your ears. That is a major step in a singer's development. To control the sound you must have both a physical feeling of your voice and, quite separately, to hear it. That is the big difference. And it is harder to do with the voice than with the piano, for instance, because of the words and the emotions that are behind it."

How long, then, will Schwarzkopf continue? "As long as I have my ears."