This musical example shows that save for the lowest note of the bass voice and the three highest of the soprano, the male and female compass parallel each other at an interval of an octave apart, and that the division of the registers is the same for both.
Still utilizing the same musical example, but noting now the two chief divisions of male and female voices (bass and tenor in the male and alto and soprano in the female), the example would be divided as follows:
It must be borne in mind that registers overlap, that they extend up and down one into another, and that at points where this occurs it is optional with the singer in which of the two overlapping registers he will produce his tones. There are many singers who can sing at will the lower half of the middle register either in chest or middle, and the upper half of the middle either in middle or head. It is to be noted, however, that it is easier to bring down a tone from a higher into a lower register than to force up a register, the latter proceeding often being ruinous to the voice.
Duprez, a phenomenal tenor, could, as I have stated, sing the whole tenor range in the chest register. He could emit the ut de poitrine, which means that he could sing even tenor high C in the chest register. The result was that half the tenors of Europe ruined their voices trying to imitate him. For they ignored the natural three-register divisions of the voice, and thought they could accomplish with their average voices what is reserved only for phenomenal ones.
There are three registers; and the interrelations between these and the different voices within the male and female range must now be considered.