Every tone in singing usually takes the sound of some vowel.
By the greater or less distinctness of one or another of the
over-tones, sounding with the fundamental tone, various timbres
of the vowel are produced. But certain vowels in certain parts
of the scale can be sung far more easily and sweetly than
others. The investigation of this fact has taught us that
a tone gains in richness when the tone corresponding to the
vowel belongs to the over-tones of the fundamental tone. In
the human voice, however, the tones favorable to the several
vowels do not admit of being precisely determined.
In different languages and dialects the vowels have different
shades, and a scarcely perceptible variation, especially in the
clearer vowels, is sufficient to cause the over-tones to be heard
more or less distinctly. After I had learned, with the kind
assistance of Professor Helmholtz, by means of his artificial
apparatus for the sharpening of the ear, to find out over-tones
and to know their peculiarities, I was soon able, without any
artificial help, to discover the vowels favorable to them by the
fuller sound of certain tones. In the female voice all tones below
the c¹ take the character of _o_. At the c¹, _a_, pronounced as in
the English word _hall_, sounds the best, and at d♯¹ e¹ passes in
to _a_, as in _man_, and at f¹ into _a_, as in _may_. With the g¹
the _a_ sounds again as in _man_; a¹ b♭¹ b¹ c² are favorable to
all the vowels, while d² e♭² e² sound best with _e_. After e²
every tone takes the coloring of _a_, as in _father_, and sounds
well only with this vowel; b♭² c³ d³ sound again better with _e_.
As thus, above e² f² all the tones take the coloring of _a_ in
_father_, so the tones below c¹ take the timbre of _o_, and the
most skilful artists are not able to sing all the vowels in these
tones with equal clearness and purity. The female voice, therefore,
has only a few tones more than an octave, upon which every one of
the vowels can be distinctly sung; and again, all these tones do
not afford an equally sonorous tone with every vowel.
As unfortunately our Song composers do not always keep this fact
in view, as the old Italians did, and since words with the most
unfavorable vowels often underlie the notes, it as often becomes
necessary to mingle with the unfavorable vowel something of the
sound (_Klang_) of the vowel properly belonging to the note; as,
for example, in the word “ring” upon f², to sing the _i_ with
a mixture of the sound (_Klang_) of _a_. Artists do this in
a way of which they are for the most part unconscious, and which
is always unobserved by the hearer. That in every voice there
are several tones upon which every vowel sounds well, finds an
explanation in an observation of Professor Helmholtz. The ear is
attuned to a certain tone, designated as e⁴ f⁴. To persons with
very susceptible nerves these tones are often insupportable, and
we often see dogs, whose sense of hearing is especially acute,
run howling away when the above e⁴ is struck upon a violin,
while to other tones they seem wholly insensible. But all the
tones which are accompanied by that tone as an over-tone to
which the ear is attuned, sound harmonious even with unfavorable
vowels.