I began a discussion last month about the larynx as the source of the sound in the human body. This month I'm going to continue this discussion and go into more detail about the larynx and how it functions.

Although we use the larynx to make sound while speaking and singing, the biological function of the larynx is to act as a valve at the top of the trachea. Both the false and true vocal folds come together at the top of the trachea during the swallowing process. The tongue moves back, the larynx raises up and muscle contraction moves the food away from this valve and diverts it into the esophagus on its way into the body.

Another function of the larynx is the cough. First the vocal folds close and then the abdomen contracts, building up air pressure until the vocal folds are forced open by an explosion of air -the cough. If you have ever swallowed something "down the wrong pipe", you also know that the larynx is responsible for ejecting the food and preventing it from entering your lungs. When you go through these important bodily functions, your speech is disrupted.

But just exactly how is sound produced? Well, tone is produced by the vibration of the larynx. When the intrinsic muscles of the larynx act upon the connecting cartilages, the arytenoids rotate forward and close the opening to the trachea (known as the glottis). Anytime you are not speaking or singing, the glottis is open in the shape of a triangle. The arytenoids are seperated, pointing slightly outward. The apex of the triangle is at the front.

As the intrinsic muscles act upon the arytenoids, the vocal folds come together in the center and the edges of the folds close the entrance to the trachea. Air pressure builds up as the exhalation muscles begin to contract. As the air leaves the body the vocal folds are set into motion, producing tone.

The edges of the vocal folds will touch as many times per second as it takes to produce any sound your instrument is capable of making. You have probably heard the term 'A440' used when referring to a particular pitch. What it means is that to create that pitch, something is vibrating at a frequency of 440 cycles per second; the string on a quitar or the vocal folds in your throat. I find that quite amazing!

The muscles which move the vocal folds are called the tensors, the relaxors, the adductors and the abductors. The tensors stretch and lengthen the vocal folds. The relaxors shorten and loosen the folds. The adductors bring them together and the abductors separate them. In training the voice, work is done to equalize the strength and agility of these muscles, balancing and adjusting them to produce an efficient sound that is even and strong.

The extrinsic muscles are the ones which connect the larynx to the hyoid bone, the sternum and the omo (shoulder) bone. These muscles raise and lower the larynx during the swallowing process. During the phonation process these muscles serve to anchor the larynx so that it stays at a deep and comfortable position for producing sound. As you can see, the combination of the movement of all these muscles creates sound inside where the larynx is located.

I have often heard the term "open throat" used to describe the proper vocal technique. Actually, it is a very misleading term. It implies that all the muscles are relaxed. Although in order to sing at your best you must be free from unnecessary tensions, singing is a motor function which requires the contraction of certain muscles. Every moment of phonation requires some kind of muscular activity. However, there is a great deal of difference between a toned muscle and a tense muscle. If the throat were truly open, you would not be able to sing.

Correct technique requires that you use only the muscles needed to do the job. A singer trains so that only particular muscles work and all the rest do not interfere. "Open throat" actually refers to a relaxed neck, not relaxed throat muscles.

When you first learn to sing, your entire body gets involved in the process. Your shoulders lift, your head tenses, you breathe too much, you may even make all sorts of extra noises. Since the exact muscles are as yet unaware of their special functions, the body compensates by doing whatever works. Since the larynx is not visible it takes a lot of biofeedback before a person can really feel the larynx. With time and much repetition, though, it is amazing how much of the sensation becomes concrete, describable and predictable. I'll talk more about this in next month's column. See you then!