“We often hear singers who are said to possess naturally phenomenal voices and who's voices are naturally "placed."

This description of the voices of highly gifted singers contains a germ of truth—but the truth is so garbled and distorted by the term that there is often conveyed a false and misleading impression as to ways and means of acquiring what is sought. 

The term "voice placing" as applied to tone production has a very real meaning from appearance—that is to say, the voice appears to be static both to the producer and to the hearer. The danger in the use of this particular term in the field of instruction is that the ideas concerning the constructive process of vocal development are apt to bring about misconceptions which may, and often do, offer serious obstacles to normal progress in this desired development. 

The apparent static condition—which is doubtless the original cause of the use of the term "placing" or "placement" of the voice—is not in reality a static condition. It is merely an appearance.”

“All such phenomena are directly accounted for by bone conduction, and by vibration of air in the chest cavity, but by no stretch of the disciplined imagination can it be conceived of, as having anything whatever to do with the augmentation of air waves which might influence either the volume or quality of voice.”

“Putting the voice in the head is meant to accomplish the purpose of producing it in such a manner that it will be resonant and also relieve the throat of undue strain. It seems to be in the head, or as it is sometimes expressed, "in the mask." 

The voice properly produced naturally goes to the resonance chambers and is reflected. The phenomenon is really accounted for by the reflection of voice or air waves from the resonance cavities. 

"Things are seldom what they seem"—and the practical application is that this "seeming" must not be taken as an indication that the voice should be put in the head—for by so doing the ostensible purpose is defeated. See to it that the opening to the upper resonance cavities is not unduly restricted.”

—From Authentic Voice Production (1930) by W. Warren Shaw, student of Francesco Lamperti, William Shakespeare, and Luigi Vannuccini.  This book is not as readily available as Shaw's The Lost Vocal Art and its Restoration (1914), hence the reader is advised to seek out a good music library or search Abebooks for a copy. Its main virtue is that Shaw writes about historical vocal pedagogy teachings having benefited from an understanding of voice science.