and when these voices come down into this register they too sing with the same adjustment of the vocal tract as is used for the same tones by alto and bass. This, therefore, constitutes the lowest register for all voices—not because it consists of certain notes, but because
these notes require the same general adjustment of the vocal tract for their production by all voices.
When it comes to the next or middle register:—
for female voices (and an octave below for male voices), soprano and tenor sing through this entire register with ease, using a slightly different adjustment of the vocal tract from that which they employed when they went down into the lowest register. The ordinary alto stops at C in this register, as does also the bass at an octave lower. When they enter it their vocal tract adjusts itself to it and corresponds with the adjustment employed in it by soprano and tenor. In this register the vocal cords still vibrate along their entire length, but as the voice progresses upward, they show a tendency to shorten the glottic chink, and the cup, as well as the adjustment of the entire vocal tract, tends to become less open. It is the register of transition, placed between the lowest and highest, as if to bridge over the interval.
The highest register:
(an octave lower for male voice) calls for an extraordinary change in the adjustment of the vocal tract. The vocal cords