"Tell me," said Beverly Sills to a young singer who had just sung "Adieu, forets" from Tchaikovsky's "Jeanne d'Arc," "would you prefer to sing opera or concerts?"

Anita Berry paused, considering all the essential artistic questions involved.

She touched Sills lightly on the hand. The hand that holds up a diamond as big as the Ritz. The hand of a master. Solemnly, Berry said:

"Anything that pays."

And Sills could not help but laugh.

When Pablo Casals or Andres Segovia taught master classes to hopeful instrumentalists, the students usually remained silent, if not frozen in terror, out of reverence. But at last night's master class in front of an audience of about 200, Sills, while evincing respect, put eight students from the Wolf Trap Opera Company at ease.

Sills gently told Berry (whose voice was very fine, but whose stage carriage seemed stiff) that if she were to sing opera, she'd best learn to act. "You've got to get that audience out of their seats by the end of the performance," said Sills. "You want them to love you so much they want to get up on stage with you and hug you. That's your goal."

The teacher nearly missed class.

It was stormy weather in New York, and Sills' plane sat on the La Guardia runway for two hours. While everyone waited for her to arrive, the singers worked off a little nervousness and kept the audience at The Barns entertained by singing their backup songs, arias they would perform in case they were called upon to sing a bit more.

When Sills finally arrived, people flocked to her.

"Thank God, you made it, darling," said one woman.

"It was a trip and a half, let me tell you," said Sills, general director of the New York City Opera.

Before class began, the teacher claimed she couldn't teach: "I wouldn't be so presumptuous. It's a tremendous responsibility to help train young voices. The only thing I'd like to establish is a dialogue between these young, new artists and one old artist.

"I don't criticize, either. Just as seeing a painting is a personal experience, so is the hearing of a human voice. So what I might find to correct you might think is perfectly all right, and of course the reverse is true."

Sills, wearing an emerald green dress and lavender-tinted glasses, sat in an upholstered chair, stage right, and awaited her first student.

Lawrence Evans sang Aprite un po' from Mozart's "Marriage of Figaro."

When he was finished, the two redheads met at center stage to talk over the performance.

"How do you feel?" said Sills.

Evans looked like a man who had just escaped a pack of wolves.

"Fine," he managed to say.

Sills complimented him in general and then said, "I might make one suggestion, that in Mozart you might try to be a litle less monochromatic. If there are two identical phrases together, you should play with them, vary them in some way.

Nicholas Karousatos, from Washington, sang "Largo al factotum" from Rossini's "Barber of Seville."

Karousatos couldn't wait to get to center stage. He moved and sang as though he had been shot from a Winchester.

"You certainly have personality to burn," said Sills. "You sing very well, but you might cover up those top notes a little."

After the performance, as the audience took advantage of its chance to meet Sills and pick at a variety of cheeses and drinks provided by Wolf Trap, Karousatos admitted to a little nervousness.

"I had a dry throat," he said. "By the end of the aria I thought I might not make it."

Other company members said they were tired after rehearsing all day their upcoming production of "Regina," an opera by Marc Blitzstein based on Lillian Hellman's "The Little Foxes."

Asked if she was especially impressed with any of the singers, Sills proved herself a diplomat as well as a teacher.

"I wouldn't say," she said. "Even if I felt one way or the other, I wouldn't say. It was just fun."