There is a mother vowel, a generative tone.  It is a (Italian a).  In articulating a the mouth opens wide, giving a sound similar to a in arm.

The primitive a takes three forms.  The unaccented, Italian a represents the normal state; a with the acute accent (’) represents the eccentric state; a with the grave accent (`) represents the concentric state.

These three a’s derived from primitive a become each in turn the progenitor of a family with triple sounds, as may be seen in the following genealogical tree: 

A
A A A
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e o e

e au eu

i ou u

Eccentric.  Normal.  Concentric.

This is the only simple sound, but four other sounds are derived from it.  The three a’s articulated by closing the uvula, give the nasal an.  Each family also gives its special nasal sound:  in for the eccentric voice, on for the normal state, un for the concentric.  All other sounds are derived from combinations of these.  The mouth cannot possibly produce more than three families of sounds, and in each family it is a united with the others that forms the trinity.

The variety of sounds in these three families of vowels arises from the difference of the opening of the mouth and lips in articulating them.  These different modes of articulation may be rendered more intelligible by the subjoined diagrams: 

a is pronounced with the mouth very wide open, the uvula raised and the tongue much lowered.

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O                     O
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e, e, i and in are articulated with the lips open and the back part of the mouth gradually closed.

      /
     /
    /
    \
     \
      \

a, au, ou and on are articulated with the back of the mouth open and the lips gradually closed.

    \
     \
      \
      /
     /
    /

e, eu, u and un are articulated with the back of the mouth and the lips uniformly closed.

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The voice takes different names, according to the different sounds in each family of vowels:  the chest-voice, the medium voice and the head-voice.

These names imply no change in the sort of voice, but a change in the manner of emission.  The head, medium or chest-voice, indicates only variety in the emission of vowels, and may be applied to the high as well as the deep and medium voice.  Thus the deep voice may produce sounds in the head-voice, as well as in the medium and chest voices.

The head-voice is produced by lowering the larynx, and at the same time raising the uvula.  In swallowing, the larynx rises by the elevation of the uvula, without which elevation there can be no head-tones.