Inner and Outer Muscles
The inner muscles of the larynx (those directly connected with the action of the vocal-cords) cannot function properly and freely in producing vibration and pitch of the voice, until the outer muscles of throat and neck are busy with pronunciation and resonance of tone.
In fact, these muscles are continually in a state of elastic tension (tonacity) in connection with the rest of the body.
The inside muscles attached to the vocal ligaments and cartilages of the throat (larynx) are tensed only while producing sound. They are not used during silences.
These inside muscles are compelled to do double duty if the outside muscles connecting head with torso do not know and perform their allotted work.
Of course these neck muscles are like-wise helpless, unless those of head and torso cooperate with them.
Only when the external muscular envelope of the whole body acts as a unit, can the internal muscles of the voice, untrammeled, function.
The diaphragm is also an inner muscle that can control breath, only when the abdominal and pelvic muscles co-operate with hose of chest, neck and head.
The feeling of co-ordination from head to foot is that of being stretched in all directions at the same time.
Inner muscles act instinctively when outer muscles assist co-ordinately and continually.
From Vocal Wisdom: Maxims of Giovanni Battista Lamperti by his pupil and assistant William Earl Brown (1931).