For this reason it was proper that ah should be preferred as the practice vowel, as soon as it was placed properly between the two extremes, and had satisfied all demands. I prefer to teach it, because its use makes all mistakes most clearly recognizable. It is the most difficult vowel. If it is well pronounced, or sung, it produces the necessary muscular contractions with a pleasing expression of the mouth, and makes certain a fine tone color by its connection with oo and o. If the ah is equally well formed in all ranges of the voice, a chief difficulty is mastered.
Those who have been badly taught, or have fallen into bad ways, should practise the vocal exercise I have given above, with ya-ye-yah, etc., slowly, listening to themselves carefully. Good results cannot fail; it is an infallible means of improvement.
Italians who sing well never speak or sing the vowel sound ah otherwise than mixed, and only the neglect of this mixture could have brought about the decadence of the Italian teaching of song. In Germany no attention is paid to it. The ah, as sung generally by most Italians of the present day, quite flat, sounds commonplace, almost like an affront. It can range itself, that is connect itself, with no other vowel, makes all vocal connection impossible, evolves very ugly registers; and, lying low in the throat, summons forth no palatal resonance. The power of contraction of the muscles of speech is insufficient, and this insufficiency misleads the singer to constrict the throat muscles, which are not trained to the endurance of it; thereby further progress is made impossible. In the course of time the tone becomes flat at the transitions. The fatal tremolo is almost always the result of this manner of singing.
Try to sing a scale upward on ah, placing the tongue and muscles of speech at the same time on ā, and you will be surprised at the agreeable effect. Even the thought of it alone is often enough, because the tongue involuntarily takes the position of its own accord.
I remember very well how Mme. Désirée Artot-Padilla, who had a low mezzo-soprano voice, used to toss off great coloratura pieces, beginning on the vowel-sound ah, and then going up and down on a, ee, aüoah. At the time I could not understand why she did it; now I know perfectly,—because it was easier for her. The breath is impelled against the cavities of the head, the head tones are set into action.
Behind the a position there must be as much room provided as is needed for all the vowels, with such modifications as each one requires for itself. The matter of chief importance is the position of the tongue in the throat, that it shall not be in the way of the larynx, which must be able to move up and down, even though very slightly, without hindrance.
All vowels must be able to flow into each other; the singer must be able to pass from one to another without perceptible alteration, and back again.