Vocal pedagogues have been peddling the idea of voice placement for a very long time, perhaps the most famous being Francesco Lamperti, who taught his students to listen to the center of the head whilst singing sotto voce. 

It's a controversial concept, if only because voice science has rightly determined that the cavities of the head do not contribute to vocal tone, which is made in the vocal tract. Yet the idea has had a very long shelf life. What accounts for this? The simple answer is that singers keep talking about it, one good example being the well-known tenor Matthew Polenzani, who, when asked where he felt "words and vowels," replied: 

For me, I feel everything out in front of my eyes. Everything I do happens in this focal point [indicates just out from the eyes]. For me, the voice starts inside of the body and it ends up in front of my eyes. And in front of my eyes, this focal point, that's where the projection happens. —Leslie Holmes, "A conversation with Matthew Polenzani," Journal of Singing, Vol 63, No. 4, March/April (2007): 477

Here's the thing—and my thing about this whole thing.

Should Mr. Polenzani be robbed of his audio-vocal control—that's what we're dealing with here—because science tells him the vocal tract is the only resonator? Do his facial cavities not contribute to vocal tone? Should he stop listening to his voice in front of his eyes?

I do not believe so. Unlike some of my colleagues, I consider Mr. Polenzani's self-observation an actual phenomenon rather than a matter of self-delusion. What accounts for it? The short answer is the ear, specifically in how it processes and perceives vocal tone.

I tackled this matter head-on in my introduction to Hidden in Plain Sight: The Hermann Klein Phono-Vocal Method Based upon the Famous School of Manuel García. There, I demonstrated that García, Lamperti's great rival, recognized the "effect" of voice placement even if he focused on its "cause."  For those curious enough to read the footnotes accompanying my text, I also showed that voice science, i.e., acoustical research, is catching up with historical teachings.

Note: The "voice placer" image comes from an issue of "Musical Courier" and illustrates the lengths to which singing teachers have mistaken cause for effect.