We might say that the Italian method was a method and then again that it was no method. As a matter of fact it is thousands of methods – one for each case or vocal problem. For instance, if I were to sing by the same means that Mr. Caruso employs it would not at all be the best thing for my voice, yet for Mr. Caruso it is without question the very best method.

I should say that the Italian vocal teacher teaches, first of all, with his ears. He listens with the greatest possible intensity to every shade of tone-color until the ideal tone reveals itself. This often requires months and months of patience. The teacher must recognize the vocal deficiencies and work to correct them.

For instance, I never had to work with my high tones. They are today produced in the same way in which I produced them when I was a boy. Fortunately  I had teachers who recognized this and let it go at that.

[…]

Possibly the worst kind of a vocal teacher is the one who has some set plan or device or theory which must be followed “willy-nilly” in order that the teacher’s theories may be vindicated. With such a teacher no voice is safe…The good sense of the old Italian Masters would hold such a plan up to ridicule.

Great Singers on the Art of Singing: Educational Conferences with Foremost Artists. Theo. Presser Company, 1921.