If you have an attack of inflammation or cold further down, and the vocal bands swell, or the mucous membrane lining the voice box becomes inflamed and thickened, then the voice is lost entirely, just as the tone of a violin would be if a wet cloth were thrown across the strings. But disturbances in the voice box, or larynx, cause only a very small percentage of husky, poor, or unmusical voices.
A far commoner cause, indeed probably the commonest single cause of a poor, squeaky, or drawling, unmusical voice is careless and improper management of the mouth and lips. In the first place, you can easily show that such marked differences in sound as those of the different vowels are all produced by the mouth and lips. If you will prepare to say the vowels—a, e, i, o, u—aloud, and begin with a, and then hold your mouth and lips firmly in the same position, you will find that all the other vowels also come out as a. If, on the other hand, you begin with your mouth and lips in the rounded and somewhat thrust-out position necessary to say o, and try to repeat the rest of the vowels, you will find that you cannot say them at all, but only different forms of o. When you have convinced yourself of this, repeat the vowels loudly and clearly without stopping to think about the position of the mouth, and notice how your lips, the tip and base of your tongue, and your soft palate and throat all change their positions for each successive vowel.
If you will try to sing the scale, beginning with a comfortable note about the middle of your voice range, and letting your mouth take the shape for that note unconsciously, you will find that, as you sing up the scale, you change the shape of your mouth, lips, and tongue at every note, thrusting the lips and mouth further forward as if to whistle, narrowing the opening and closing up the back of your throat for the high notes.
On the other hand, as you sing down, you tend to open the mouth and lips more widely, to drop the bottom of your mouth—that is, the base of your tongue—toward your throat, and your chin down toward your chest. Again you will find, just as in the case of the different vowels, that you can sing any tone clearly and musically after putting the mouth in precisely the shape that best fits that tone; and learning how to do this is a most important part of vocal training.
What we call words are simply breath sounds and voice-box sounds chopped into convenient lengths by the movements of the tongue and lips and throat. So when we come to the question of clear and pleasant speaking, or, as we term it, articulation, the lips and tongue have almost everything to do with making the difference between a clear, musical, and refined enunciation, which is so easy to understand that it is a pleasure to listen to it, and a slurred, drawling, squeaky, nasal kind of speech, which is as hard to understand as it is unpleasant to listen to.
Few of us can ever hope to develop a really great singing voice; but anyone who will take the pains can acquire a clear, distinct, and pleasing speaking voice; and perhaps half of us can learn to sing fairly well. But to do this, we must first have good, healthy, well-developed lungs and elastic chest walls, which can come only from plenty of vigorous exercise in the open air, combined with good food and well-ventilated rooms. We must have a healthy stomach, which will not fill up with gas and keep our diaphragms from going down and enlarging our chests properly; we must have clear nasal passages, good teeth, well-shaped mouths and flexible lips, which we are willing to use vigorously in articulating, or cutting up our voice sounds; and we must have good hearing and a well-trained ear. In short, the best way to get a clear, strong, pleasant voice is to have a vigorous, well-grown, healthy body.