sters for
men and women is due to the fact that men's voices run parallel to those
of women at an interval of an octave below, and that, note for note, the
adjustment of the male vocal tract is the same as that of the female
vocal tract an octave above. For this reason basses and baritones,
although singing an octave below contraltos and altos, sing in the same
registers; for this reason also, tenors, although singing an octave
below sopranos, employ the same registers. I am, of course, speaking
of average voices, not of phenomenal ones.

Mackenzie has defined a register as a series of tones of like quality
producible by a particular adjustment of the vocal cords. Mills defines
register as a series of tones of a characteristic clang, timbre, color
or quality due to the employment of a special mechanism of the larynx in
a particular manner. Both definitions practically mean the same thing.
What I object to in them is their use of the word "quality," and
Mackenzie's limitation of the adjustment to the vocal cords and Mills'
to the larynx. The adjustment takes place throughout the entire vocal
tract. Indeed, one of the claims I make for this book is, that it does
not limit the voice-producing factor to the vibrations of the vocal
cords, but while recognizing the importance of these, also considers
the importance of the rest of the vocal tract in relation to them. Other
writers hold that voice is produced solely by the vibrations of the
vocal cords, and that the rest of the vocal tract is concerned merely
with determining the timbre of the voice. But I do not limit the
function of the vocal tract below and above the cords simply to voice
quality. To produce a given tone requires not only vibration of the
cords but an adjustment along the entire tract and especially a
change in the size and shape of the cup space. If one wished to be
exasperatingly accurate one might say that each adjustment constituted
a register, and that in every voice there were as many registers as there
are tones. But surveying the progress of the voice up the vocal scale,
and as a whole, it is found that up to a certain point the general
character of adjustment within the vocal tract is the same, that
beyond that point there is a change to another adjustment of a general
character, and further beyond still another--in other words, that there
are three registers.

Some writers recognize only two physical changes in the mechanism of the
vocal tract an