I attended the master class at The Juilliard School where Joan Sutherland, when asked about her vocal technique, replied that it was described by Herman Klein in an essay titled 'The Bel Canto' in Herman Klein and the Gramophone.

Boy, did my ears perk up! I went to the New York Public library the next day to find the book.

What is most interesting about Klein's essay—The Bel Canto: with particular reference to the singing of Mozart—is that it adds to Manuel Garcia's writings in a significant way. To put matters simply: while Garcia concerned himself with 'cause', Klein addressed 'effect'.

(b) Resonance

The old Italian teachers had no trouble in obtaining a bright ringing tone. 'Resonance,' therefore, may not have entered very largely into their theory, but was far from being ignored in their practice. Thanks chiefly to their 'open' vowels an easy 'forward' tone came naturally to the majority of their students, especially the native ones. If it did not, the masters opened their pupils' throats (temporarily at least) until the sounds-waves had learnt to find their way to every facial cavity or space (besides the mouth) that was capable of 'reflecting' a vocal tone. The idea seems simple enough. The voice, in order to acquire its full vibrant power, must have the aid of a 'reflector', just as surely as the light burning in a lighthouse. The singer can no more dispense with its aid than a performer on the piano or the violin could dispense with that of a sounding-board.

As the act of singing is a natural organic function, common to the majority of civilized people, there is no need to discuss here the physiology of tone production. The point is, rather, whereabouts is that tone situated or sounding when it has left the larynx? The answer is that a clear note is, at the moment of its utterance, instantly ringing clear and true in its ultimate position, projected and maintained there by steady diaphramatic breath-pressure, and enhanced in strength and colour by shape and other influences. To the singer the resulting sensation is that the tone is coming not from the throat at all, but existing ready-made in the area to which is is reflected.

Free, unobstructed access to these 'forward' cavities can alone enable the voice to obtain all the advantages of complete resonance. Properly directed and well supported by the breath, it can entirely escape the danger of a nasal quality and attain increased beauty of timbre, diversity of colour, and penetrative power.

(c) Vowel-Formation and Attack

The formation of some vowel shape must necessarily precede the attack of a vocal sound- an act which involves the opening of the mouth. If we sing with the mouth shut we hum; but the act of humming is not without its use as a means for indicating where the vibration of the sound-waves may be felt re-echoing in the facial resonators when unable to make their exit by the ordinary route.

When we open the mouth to sing a note, it must be done by dropping the lower jaw, and without moving the head, which remains erect and still. The tongue flattens as the jaw descends, whilst the pharyngeal space at the back of the throat enlarges into a dome or arch. The shape thus created gives us, without further preliminary action, the natural mould for the formation of the universal vowel sound 'ah' - that is, the first vowel of the Italian alphabet.

The formation of all other vowels, no matter what the language, is simply a variation on this fundamental process, although the sense of their location seems to the singer to be different, with different vowels. In reality vowel sounds should all feel alike, to the extent that they feel so when we speak them. Only, some vowels create a more naturally 'forward' position than others, and those that do not must, by correct treatment, be made to acquire an equal degree of resonance.

The outcome of this assimilation is that the singer finds both tone and vowel impinging upon the same identical facial area, that is to say, in the 'mask'; and there alone, will their union be made perfect. In no other fashion and by no other mechanical means can 'speech and song' be resolved into a single function.

The science-minded vocal pedagogue reminds the reader that the nasal passages do not contribute to the tone that originates in the larynx. Therefore the thinking goes: it is futile to concern one's self with 'forward' placement. ‘There is no there there, to quote Gertrude Stein. Klein confounds this reasoning when he states later on in the text: "Therewith, not in the throat nor with any perceptible action of he glottis, but in the ultimate 'forward' area to which it has been projected, does the attack of the vocal tone actually begin."

Now isn't that a kicker?  The School of Manuel Garcia—The Christopher Columbus of the larynx—taught voice placement. 

The read the entire essay, click on the book titled Herman Klein and the Gramophone in the first paragraph and search the book for 'The Bel Canto.'