The Human Voice... According To WIKI

Actually, before I jet off to Hawaii for the weekend to party with Britney, Mariah and Beyonce I thought I'd whack up some Wikipedia bumph about the human voice... it just helps with a little technical stuff. 

In its physical aspect, singing has a well-defined technique that depends on the use of the lungs, which act as an air supply, or bellows; on the larynx, which acts as a reed or vibrator; on the chest and head cavities, which have the function of an amplifier, as the tube in a wind instrument; and on the tongue, which together with the palate, teeth, and lips articulate and impose consonants and vowels on the amplified sound. Though these four mechanisms function independently, they are nevertheless coordinated in the establishment of a vocal technique and are made to interact upon one another. During passive breathing, air is inhaled with the diaphragm while exhalation occurs without any effort. Exhalation may be aided by the abdominal, internal intercostal and lower pelvic muscles. Inhalation is aided by use of external intercostals, scalenes and sternocleidomastoid muscles. The pitch is altered with the vocal cords. With the lips closed, this is called humming.

The sound of each individual's singing voice is entirely unique not only because of the actual shape and size of an individual's vocal cords but also due to the size and shape of the rest of that person's body. Humans have vocal folds which can loosen, tighten, or change their thickness, and over which breath can be transferred at varying pressures. The shape of the chest and neck, the position of the tongue, and the tightness of otherwise unrelated muscles can be altered. Any one of these actions results in a change in pitch, volume (loudness), timbre, or tone of the sound produced. Sound also resonates within different parts of the body and an individual's size and bone structure can affect the sound produced by an individual.

Singers can also learn to project sound in certain ways so that it resonates better within their vocal tract. This is known as vocal resonation. Another major influence on vocal sound and production is the function of the larynx which people can manipulate in different ways to produce different sounds. These different kinds of laryngeal function are described as different kinds of vocal registers. The primary method for singers to accomplish this is through the use of the Singer's Formant; which has been shown to match particularly well to the most sensitive part of the ear's frequency range.

So, now you know, thanks Wiki! 

Signing out... :)