But what makes an excellent voice teacher? Do all singers need teachers (who work on fundamental issues of vocal technique) or will a vocal coach (who generally works with a singer on a specific piece or kind of repertory) yield better results?

"The bottom line," says Craig Rutenberg, the Met's director of music administration, "is, How do I sound?" We've assembled a decidedly non-comprehensive list of some of the most influential coaches and teaching approaches.

Former Stars

The road from singer to teacher is a natural one, but it doesn't guarantee success. Some top performers, however, also possess the teaching gene. Mirella Freni's career as a soprano lasted for decades, largely due to her rock-solid technique, which she now shares with students at her school in Vignola, Italy.

Soprano Renata Scotto was a fierce and dramatically gripping artist; as a teacher with her own academies in Rome and outside New York City, she is well known as an uncommonly generous and knowledgeable instructor, who often works with young artists at the Met.

Famed for her portrayal of Cio-Cio-San in Puccini's Madama Butterfly, Diana Soviero is another singer who has turned her musical talents to instruction (and who also works with young Met artists), with a focus on marrying dramatic intensity and beautiful vocal performance.

Tenor Carlo Bergonzi has his own academy in Bergamo, Italy, where Salvatore Licitra studied, as well as his own singing contest.

Swedish baritone Hê‰kan Hagegê‰rd was known internationally for his portrayals of Papageno in Die Zauberfl‹te, Wolfram in Tannh‹user, and others; today he is a prominent coach in the art of lieder.

"There's a sense among older artists that this is something they need to do to help keep the art form alive," says Lenore Rosenberg, the director of the Met's Lindemann Young Artist Development Program. "They want to pass along what they know — you can't really learn it any other way."

Met Opera Coaches

"My priority is absolute beauty of sound," Rutenberg says of his coaching approach. "Do not go for an ugly or dramatic sound just for the sake of being dramatic. Know what your idea of the most beautiful sunset is, and that's your most beautiful singing. Then, from there, go for the effects and the color and the drama. But I think you need to start with a great, round, and well-supported sound."

Rutenberg has worked with such singers as Thomas Hampson, Ben Heppner, Susanne Mentzer, and Christine Brewer in their quests to achieve maximum vocal beauty. And at the Met, he is supported by a vast network of world-class coaches, prompters, and rehearsal pianists, all of whom work with the company's full roster of singers. Coach John Fisher (formerly the Met's head of music, now the general manager of the Welsh National Opera) is known for teaching James Morris the role of Hans Sachs in Die Meistersinger; Robert Morrison specializes in German repertory; and Joan Dornemann has her own international teaching program, with outposts in Israel, Puerto Rico, Canada, and France. Other major Met coaches include John Beeson, Steven Eldredge, Dennis Giauque, and Donna Racik, among many others.

Famed Teachers

The custodianship of a singer's technique is a major responsibility, especially since many teachers work with performers from a young age, when they're especially open to influence.

Ruth Falcon is a legend in the field and works with such starry students as Andrea Gruber, Sondra Radvanovsky, and Deborah Voigt. Falcon is known for being adept at harnessing huge voices, but she is just at home working with smaller-voiced singers.

Patricia McCaffrey, of the Manhattan School of Music, is another star teacher, who works with Patricia Racette and Michelle DeYoung; Mark Oswald, a former singer who stopped performing at a fairly young age, is now a respected teacher who works often at the Met; Marcello Giordani's teacher, Bill Schuman, also works with musical theater artists and is in demand internationally.

The Met's Rutenberg calls star teacher Marlena Malas "a great colleague and a great woman," adding of her approach to proper technique, "If you think Sutherland and Pavarotti are great singers, then Malas is for you."

The International Set

For help with specialized repertory, a number of European coaches are among the world's most sought-after coaches. Denise Mass_ and Pierre Vallet are the French repertory coaches of the moment. Robert Kettelson of the Paris Opera, Ann Beckman in Zurich, and the Mariinsky Theatre's Irina Soboleva are important figures on the global coaching scene. And another top coach has a Met connection: the Mariinsky's Larisa Gergieva, who notably worked with Olga Borodina, is the sister of the Met's Principal Guest Conductor, Valery Gergiev.