The longer I teach the art of bel canto, the more I observe the teaching of singing isn't a complicated matter.

It's actually quite simple, involving—at most—five or six things. Does that make it easy? Well, that depends on who you are. Singing, like learning a foreign language, is easier for some people than others. Simply put: you have to have an ear for it. Sure. Plenty of people can kinda-sorta read a newspaper in  French or Italian, but they have a devil-of-a-time holding a conversation in either tongue, which simply shows the ear is woefully underdeveloped. 

What are the sounds of singing? Historically speaking, they are the tonal values contained within the Italian language. I teach them to all my students by example. No, I don't teach Commercial Contemporary Music students to sing in Italian! That's not the point.

Rather, I teach everyone to listen to their vowels which shapes their listening ability, Italian tonal values being the most effective means.

Most of the time, I don't even say what I am doing. Why? I avoid confusing students with theoretical and technical mumbo-jumbo. Sure, I can tell a student how to shape his tongue for /i/, /e/ and /a/. But asking them to put the tongue in a certain position is never as effective as having them model a clear example of the vowel and then observe where the tongue lies. That's the curious thing which many do not understand: the intention to communicate clearly creates the  physiology which supports it, not the other way around. 

How does this manifest itself in the studio? Let's take /i/ as example. Using the the terminology of the old school, most Americans speak and sing /i/ through a "closed throat." The mechanistic voice teacher might think this means the throat should be distended. But that is not what the old school meant. What they were talking about was the auditory sensation that is experienced by the singer and listener. Of course, the student needs a teacher to figure out exactly what this means. It is learned behavior, and is a result of replicating sounds that are demonstrated by the teacher. This was how it was done in the 18th century when Nicola Porpora was teaching. This is also how language is learned: from the audition of the mother's voice in the womb, to repeated exposure to language once the child is born.

It takes more than a knowledge of anatomy and physiology to teach singing. To teach singing in a highly effective manner, you really have to be able to sing, and know the sounds that make up singing, as well as be able to demonstrate them to your students. 

Adelina Patti was once asked what she did when she was singing. She replied that she had no idea. What she neglected to say was that both of her parents were singers, and that she learned to "speak" singing at an early age. Something does not come from nothing: you have to "get" singing from someone. For me, it was hearing Julie Andrews sing when I was a kid. My mother also sang in a clear beautiful voice. As a boy soprano, I wanted to know—had to know actually—how both of them did that. Is it any wonder I grew up to be a voice teacher?