The vocal cords for a =vibrator=.
3.

The throat, mouth, and the nasal and head cavities for a =resonator=.
4.

The tongue, lips, teeth, and palate for an =articulator=.
These elements appear in as great a variety of size and proportion as do the variations of individual humanity, and each element is, moreover, variable according to the will or feeling of the individual.
This susceptibility to change constitutes a modifying power which gives a variety in tone quality possible to no other instrument and makes it our wonder and admiration.

The modification and interaction of these various parts produced by the emotions of the singer or speaker give qualities of tone expressive of the feelings, as of pain or pleasure, grief or joy, courage or fear.
[Illustration: FIGURE 1 .-- Section of the head and throat locating the organs of speech and song, including the upper resonators.

The important maxillary sinus cannot well be shown.