“The low notes of the falsetto show the glottis infinitely
better than the unisons of the chest voice, and produce
vibrations more extended and more distinct. Its vibrating
sides, formed by the anterior apophyses of the arytenoid
cartilages and by the ligaments, become gradually shorter as
the voice ascends; at the notes la si (a¹ b¹) the apophyses
take part only at their summits; and in these notes there
results a weakness similar to that which we have remarked in
the chest notes an octave below. At the notes do re (c♯² d²),
the ligaments alone continue to act; then begins the series of
notes called the _head voice_. The moment in which the action
of the apophyses ceases exhibits in the female voice a very
sensible difference to the ear and in the organ itself. Lastly,
we verify that up to the highest sounds of the register the
glottis continues to diminish in length and in width.
“If we compare the two registers in these movements, we shall
find some analogies in them; the sides of the glottis formed
at first by the apophyses and the ligaments become shorter
by degrees, and end by consisting only of the ligaments. The
chest register is divided into two parts, corresponding to
these two states of the glottis. The register of falsetto-head
presents a complete similarity, and in a still more striking
manner.
“On other points, on the contrary, these same registers are
very unlike. The length of the glottis necessary to form
a falsetto note always exceeds that which produces the unison
of the chest. The movements which agitate the sides of the
glottis are also augmented, and keep the vibrating orifice
continually half opened, which naturally produces a great
waste of air. A last trait of difference is in the increased
extent of that elliptic surface.
“All these circumstances show in the mechanism of the falsetto
a state of relaxation which we do not find in the same degree
in the chest register.