The voice is equalized by the proper ramification of the breath and the proper connection of the different resonances.
The tone is colored by the proper mixture of vowels; _oo_, _o_, and _ah_ demanding more palatal resonance and a lower position of the larynx, _a_ and _e_ more resonance of the head cavities and a higher position of the larynx. With _oo_, _o_, _ü_, and _ah_ the palate is arched higher (the tongue forming a furrow) than with _[=a]_, _[=e]_, and _ü_, where the tongue lies high and flat.
There are singers who place the larynx too low, and, arching the palate too high, sing too much toward _oo_. Such voices sound very dark, perhaps even hollow; they lack the interposition of the _[=a]_,--that is, the larynx is placed too low.
On the other hand, there are others who press it upward too high; their _a_ position is a permanent one. Such voices are marked by a very bright, sharp quality of tone, often like a goat's bleating.
Both are alike wrong and disagreeable. The proper medium between them must be gained by sensitive training of the ear, and a taste formed by the teacher through examples drawn from his own singing and that of others.
If we wish to give a noble expression to the tone and the word, we must mingle its vocal sound, if it is not so, with _o_ or _oo_. If we wish to give the word merely an agreeable expression, we mingle it with _ah_, _[=a]_, and _[=e]_. That is, we must use all the qualities of tonal resonance, and thus produce colors which shall benefit the tone and thereby the word and its expression.
Thus a single tone may be taken or sung in many different ways. In every varying connection, consequently, the singer must be able to change it according to the expression desired. But as soon as it is a question of a _musical phrase_, in which several tones or words, or tones alone, are connected, the law of progression must remain in force; expression must be sacrificed, partly at least, to the beauty of the musical passage.
If he is skilful enough, the singer can impart a certain expression of feeling to even the most superficial phrases and coloratura passages. Thus, in the coloratura passages of Mozart's arias, I have always sought to gain expressiveness by _crescendi_, choice of significant points for breathing, and breaking off of phrases. I have been especially successful with this in the _Entführung_, introducing a tone of lament into the first aria, a heroic dignity into the second, through the coloratura passages. Without exaggerating petty details, the artist must exploit all the means of expression that he is justified in using.