Thanks to your downward letting-go accompanying your exhalation, your flexible triggering of your inner vibration propels rich vocal harmonics, consuming very little air which you can imagine or feel like it were recycling within the body, at the diaphragm center.
The two lower vocal cords are drawn together and vibrate through emission. The vibration is caused by air passing across the cords. The volume of air is so small that it seems almost spontaneous and automatic as with speech. The brain essentially regulates the tension of the vocal cords to keep the flow of air at a minimum, so that the vibration corresponds to the desired pitch.
Whenever the thorax contracts prematurely, it prevents the diaphragm from functioning to its full extent.
(…) In order to avoid pushing when you sing, you need to notice certain proprioceptive sensations.
You must learn to conserve stored air and to give out the least possible amount, as if you were distilling the sonic flow in some way. (…) The more slowly and regularly the flow emerges, the less underlying tension results, and the more easily the larynx works.
The great art consists of not pushing, of remaining in a state of supple tension, and of avoiding undue muscular effort.
Alfred Tomatis, The Ear And The Voice
(translated by Roberta Prada and Pierre Sollier)