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. PARTIAL TONES