The basis of all vocal sounds is the column of air that you send up from your lungs. The lungs act as bellows that push air through the windpipe into the larynx, or voice box, which is in the middle of your throat. Inside your voice box, on opposite sides, are two tiny folds of muscle called vocal cords. These are the main sound producers. These folds of muscle open and close the air passage through the larynx to let air in and out as well as to keep unwanted objects out of the lungs. In normal breathing no sound is produced as air passes over the vocal cords. But when a person wishes to speak, muscles tighten the vocal cords, and these vibrate as air from the lungs is forced past them. This results in sound.
The tighter the vocal cords are stretched, the faster they vibrate and the higher the tones of the sounds produced. On the other hand, the more relaxed the cords, the lower the tones. After leaving the larynx, the sound wave enters the upper part of the throat, called the pharynx. Then it passes into the mouth and nasal cavity. There overtones are added that modify, amplify, and reinforce the fundamental tone. The roof of the mouth as well as the tongue, teeth, lips, and jaw combine to break up the vibrating waves of sound, which come out in the form of understandable speech.
The human voice is a marvel, unequaled in versatility by any man-made instrument. It has the ability to express feelings and emotions ranging from tender, gentle love to harsh, violent hatred. When properly developed and trained, the voice can cover a range of as much as three octaves and can deliver not only beautiful musical sounds but also heart-stirring patterns of speech.