specific muscular contractions concerned in the
rotation of the arytenoids have not been located.

It is generally asserted by vocal theorists that the quality of the
vocal tone, on any one note, is determined mainly by the influence of
the resonance cavities. Dr. Mills says on this point: "When it is borne
in mind that the vocal bands have little or nothing to do with the
quality of the tone, the importance of those parts of the vocal
apparatus which determine quality... becomes apparent." (_Voice
Production in Singing and Speaking_, 1906.) This theory that the quality
of the tone is determined solely by the resonance cavities is directly
contradicted by Prof. Scripture. He proves that changes in tone quality
result from changes in vocal cord adjustment. This subject is more fully
treated in the following section. Even before this matter had been
definitely settled by Prof. Scripture, there was a strong presumption in
favor of the vocal cord adjustment theory. Howard advanced this idea in
1883. Several empirical observations support this theory. Most important
of these is the fact that a single tone, swelled from _piano_ to
_forte_, goes through a wide variety of changes in quality.
Stockhausen's mention of this fact has already been noted.

This fact tends to cast some doubt on the value of laryngoscopic
observation as a means of determining the laryngeal action. Under the
conditions necessary for examination with the laryngoscope it is
impossible for the singer to produce any but soft tones in the head
quality of voice. Most of these tones, if swelled to _forte_, would
change from the head to the chest quality. It is probable that this
change in quality is effected by a corresponding change in the vocal
cord adjustment, as the conditions of the resonance cavities remain the
same. But this cannot be determined by laryngoscopic observation.

So far as the actions of the laryngeal muscles are concerned, no
difference can be defined between the correct vocal action and any
improper mode of operation. Sir Morell Mackenzie examined a large number
of people with the aid of the laryngoscope; of these, some were trained
singers, others, while possessed of good natural voices, had had no
vocal training whatever. Many variations were noted in the notes on
which changes of register occurred. But it could not be determined by
this mode of examination whether the subject was a trained singer or
not.

If there is one specifical