VOWELS
All speech sounds are made by air as it is expelled through the voice box or larynx, the mouth, and the nose. If the air sets the vocal cords into vibration and passes out the mouth without obstruction or hindrance, sounds known as vowels result.
Quality, or kind of vowel, is affected by the way breath sets the vocal cords into vibration and the way it is used in the resonators above the larynx, as well as by the size and shape of the cavities through which it passes.
It is apparent that sound is modified by even slight changes within the voice box and the resonators, for example, such as those brought about in the oral cavity by movement of tongue, lips, and jaw. These changes make possible the variety of vowels needed to speak any language.
Say the following words slowly and distinctly: calm, not, past, all, care, man, fate, met, pin, girl, home, borne, cup, boot, cook. You may perchance pronounce some of the vowels exactly like others. There are people, however, who would make a fine distinction in them. Although you may not form all the sounds possible, you should notice that those you do say are distinctive in quality and are formed in different ways.
The vowel ah has a different color or timbre than ee, oo than ay, and so forth. In some sounds the lips are rounded, in others they are spread, forming a narrow opening; in some, the front of the tongue is raised toward the roof of the mouth; in others, the back of the tongue may be the highest part, or it may lie quite flat in the mouth, Sometimes the lower jaw may be dropped, so that there is considerable width between the teeth, or it may be raised so that the mouth is open only a little. However, despite these differences, you will observe that vowels have certain characteristics in common.
For all of them the vocal cords must vibrate, and the throat and mouth resonators must be unobstructed. To form them correctly the breath stream must be steady and controlled, and the tongue, lips, and jaw must be flexible. Better vowels, and therefore better voice quality, are obtained if the tip of the tongue is kept near the inner surface of the lower teeth. Notwithstanding the fact that each vowel has its distinctive quality, you should produce them in such a way that all sound as if made by the same instrument. As a rule, the mouth is more open in singing than in speaking, and the higher the pitch, the more open does it become. You should hear in mind that the singing tone is a vowel and that its form must be sustained until the next element in the word is due. By that is meant that, if the articulatory organs move during the prolongation of sound, the quality of the vowel is altered.
Since the vowel is the main vocal element in speech and song, the voice depends largely upon it for beauty, strength, and expressiveness. Therefore it is implicit that well-sung vowels increase the resonance and musical quality of the voice. In singing, practice or vocalizing is done mainly on the sounds ah, ay, ee, oh, oo, often called the primary vowels, for other vowel sounds are considered modifications of them. You should, however, give thought to singing the various kinds, for all occur frequently in both song and speech.