I went to the Metropolitan Opera last night to hear Mozart's opera Idomeneo with Matthew Polenzani in the title role. He was in top form. Of course, I woke up thinking about how one sings Mr Mozart. We learn something about that from a conversation between Bruce Duffie and Margaret Harshaw—the doyenne of voice teachers—that you can find online here.
BD: Is there a secret to singing Mozart?
MH: Yes, there certainly is. It requires the most pure placement of the voice, and for that reason it’s very difficult to sing.
BD: And yet that’s what is imposed on a lot of youngsters.
MH: Yes, and I will say I don’t think that’s always the wisest thing, because they will sing it by manufacturing, or singing it in a small voice. You have to sing it with a real voice that is well controlled, which is different, and in a very high placement, but not high larynx — there’s the difference.
BD: Getting back to roles a little bit, is it right to impose both Mozart and Wagner on the same voice?
MH: The reason I sang Mozart was to keep my voice from falling lower and lower, getting thick and heavy, and not being able to get to the top notes — which is what the older singer fights. If you sing Mozart, it keeps you in that high position. It isn’t easy, but there it is again; if you want something, you will work for it, and that is the reason I sang it.
Pure placement. High placement. High position. These are descriptive terms you won't hear outside the voice studio, and even within the studio, the student can only understand their meaning through demonstration/feedback from a great listener as well as auditory sensation. These terms have their root in the García School of Singing, which has also been described in brief by Margaret Harshaw—who studied with Anna E. Schoen-René, herself a student of Pauline Viardot-García and Manuel García—as involving low support and high placement.
For practical information on voice placement, see my book Hidden in Plain Sight: The Hermann Klein Phono-Vocal Method Based upon the Famous School of Manuel García in the right-hand column.