Each of us was born with an inborn capacity to breathe. Perfect breathing, i.e. with maximum energy efficiency: maximum results with minimum effort. Then, around the age of 3/6 years, when our mind begins to become more relational and less instinctive, the brain begins to take over and to put in place unconscious processes that outweigh the natural breathing with a less efficient one.
In that age we unconsciously quit our posture and natural breathing to move to a more contracted and rigid one. In fact, in that period we discover that stiffening the posture and the diaphragm, not by chance also called the emotional muscle, attenuate the perception of emotions and fears at a visceral level (what we all refer as "belly").
The more a child is "afraid" of his or her internal feelings, without someone to explain that it is the normality of being alive, the more his or her vocal expressiveness will be sacrificed so as not to "listen" to these bad feelings anymore.
Too often I hear about breathing in terms that are even absurd, sometimes I find people convinced that the diaphragm is a voluntary muscle and can even make sounds!
Breathing is at the base of the voice. Voice is born with the breath. Often you hear about "throat voice" or "diaphragmatic voice", but in reality the voice is always produced by the phonatory apparatus and supported by the flow of air produced by the diaphragm.
It's easy to identify the phonatory apparatus: it's what you hear moving every time you swallow. Recognizing the diaphragm is not so simple: it is not able to produce any sound and is located inside the trunk to divide the lungs from the bowels.
When we speak of a human being, we almost never worry about the amount of air available, but about he/she manages the pressure that sustains the vibrating of the vocal cords. The secret of a good voice lies in knowing how to dose and direct the air that supports the words we say. Depending on the errors in the amount of air or in the more or less strong supply of the vocal cords, all the possible existing phonatory defects are identified, sometimes erroneously considered as " qualities " by unscrupulous voice teachers.