Can you sing with bad posture? With the best posture, you get the best voice. Vocal quality is directly affected by breath control. Breath is accessed when your body is relaxed and aligned for free energy flow. Free energy flow happens when the body is at rest. Rest is achieved in balanced position—straight line of laying down, an equilibrium of balance.
We know from physics that curves and kinks create unequal weight distribution. Contrary, straight line is balanced and accessible, in union with itself. When we feel sick, our voice takes on a murky quality. Our voice also changes according to whom we speak: to a grandmother, lover and child. The inflections are completely different according to the situation and mood.
Therefore, through physics and natural observation, the voice is a natural indicator of how balanced oneself is. The balanced state fluctuates through life events, constantly reflecting the nature and nurture of the moment revealed.