This may seem at first sight altogether incredible. To understand how the voice can be trained, without ever departing from the natural manner of singing, we must see in the first place just what natural singing is.  What takes place when I sing naturally? Suppose I sing a scale, do, re, mi, etc., just as a schoolboy does, without thinking of how he does it. I can do this perfectly well. True, I know that the vocal tone is produced by the pressure of the expired breath against the vocal cords, and that the pitch of the note is determined by the degree of tension of the cords. But I can forget all this while singing the scale, and just simply sing. Now suppose I sing the same scale again, this time making my voice sound nasal. All I have to do is to think a nasal quality of sound, and then to sing that sound. Here again, I know that the nasal quality is caused by my contracting my nasal passages and then forcing the tone through them. But I could sing the nasal tones just as well, before I ever thought of wanting to know how they are produced.

Once more let me sing my do, re, mi, scale, this time giving my voice as fine, rich, full, and musical a quality as I can. My study of vocal science has taught me that a quality of this kind is produced when all the resonating cavities act in the proper way. But it is not necessary for me to know this in order to get the desired quality. A child utterly ignorant of vocal science could do it just as well. Provided I have a certain quality of tone in mind, my voice will produce it without my knowing or caring how it is done. 

This is what is meant by natural singing. Vocal science has shed a great deal of light on the operations of the voice. We know that each fine shade of tone quality results from some special adjustments of the vocal cords and resonating cavities. But as a result of recent scientific investigation we know something of much greater importance. We have a medium of communication through which we inform our vocal organs what kind of tones we wish to sing. This medium is the mental ear. We also possess a monitor, which tells us how well our voices obey our mental demands in producing the tones we call for – our physical sense of hearing. Natural singing is thus seen to be a rather involved operation. It includes, first, the mental conception of a tone; second, the adjustment of the vocal organs in response to the mental command; third, the actual singing of the tone; and fourth, the listening to the tone and comparing it with the mental conception.

One of these steps, the adjustment of the vocal organs, calls for special consideration. It is on this point that the modern system differs most radically from the old Italian method. According to the modern idea, it is necessary for the singer to know how the vocal organs should adjust themselves for every tone, and to see to it that the adjustments are properly made. In the natural system followed by the old masters the vocal organs are left free to adjust themselves according to their own instincts. There is a mysterious instinct located in the voice. When a tone is mentally conceived, this instinct tells the vocal instrument how to shape itself for the tone. The singer himself need to nothing to help his voice in finding the correct adjustment. Nature took care of all that when she implanted her instincts in the voice. In other words, you must tell your voice what to do, but not how to do it. It is for you to decide what kind of tones you wish to sing; guided by its own instincts, your voice will then find its own way to produce the tones you have in mind.

Taylor, David C. “Natural Singing and the Old Italian Method.” Etude Magazine, August 1916: 594.