This is a very quick entry, but also a strongly salient point ...
This is something that the majority of people, professional musicians included, do not understand. However, it is a #MusicalTruth with which well-trained singers are intensely intimate. It is our deep love of our craft that propels us forward, and brings us - eventually - to mastery of our own bodies, relative to producing sound!
To quote my own teacher, the brilliant David Jones, in NY, "90% of good technique is making involuntary…