Introduction
The human voice is a complex instrument. We have vocal cords which we can loosen and tighten, and over which we can transfer breath at varying pressures. We can change the shape of our chest and neck, the position of our tounge, and the tightness of otherwise unrelated muscles. Any one of these actions results in a change to the pitch, or volume, or timbre, or tone of the sound produced.
One important categorisation which can be applied to the sounds we make relates to the register; or the "voice" which we use. Singing Singers distinguish between notes which resonate in different parts of the body, and which have correspondingly different tonal qualities.
Chest Voice
The chest voice is the register used in everyday speech. When you talk to the person next to you in a normal voice, you can feel that the sound seems to be "coming from" your upper chest. This is because lower frequency sounds have longer wavelengths, and resonate mostly in the larger cavity of the chest. When you sing notes at the bottom of your range, you are using your chest voice.
The tonal qualities of the chest voice are usually described as being rich, full, deep, loud and strong.
Middle Voice
The middle voice, also known as the "blend", is the term used to describe the range of notes which marks the crossover between the chest and head voices. It may be a distinct change (a passaggio) or a more gradual blending. With training, many singers can choose whether to sing notes in this range in the head or chest voice.
Head Voice
The head voice is often used when we shout, or are highly excited. In these situations we tend to produce higher pitches, and these resonate in the mouth and in the bones of the skull - so the sound feels as if it is "coming from" our head. When you sing the notes at the upper end of your vocal range, you are using your head voice.
The tonal qualities of the chest voice are usually described as being sweet, balladic, lilting, and pure. It is usually more tonally precise but less loud than the chest voice.
Falsetto
Falsetto is a higher range than the head voice; it relies on completely relaxed vocal cords and may sound breathy. Imagine the Bee Gees singing "Stayin' Alive", or John Cleese playing an old woman in Monty Python; that is the sound of the falsetto voice. It is generally only used by men. It is a difficult register to sing accurately in, and it tends to be rather quiet. It also requires an uncomfortable muscle effort for many men.
It is a quite distinct range from the head voice, and generally when a singer describes their range they exclude the falsetto voice.
Finding your voices
1. Stand up.
2. As loudly as you can, say the word "hellooooooooo" (holding the "o") in your normal speaking voice. Put your hand on your chest; you should feel it vibrating. If not, try singing a little louder or lower. This is your chest voice.
3. As loudly as you can, repeat the word "helloooooo" with as high a pitch as you can comfortably sing without any special muscle effort; you should feel your chest is no longer vibrating, but instead your skull is. This is your head voice.
4. Now say "hellooooooooooo" in as high a pitch as you can, even if it feels uncomfortable and sounds silly. This is your falsetto voice.
You may find it interesting to gradually sing up your range from the bottom and feel where you cross over from the chest voice to the head voice.