What is it the voice sound? Does a voice sounds always the same and having always the same perception of physical work to start a sound?
Sound is a wave, starting from a vibrating source. A trained singer with his memory will have a complex reaction and he’ll have his body ready to make the note required and vocal folds vibrating, slightly before we put the energy and the mucosa wave that starts the sound heard outside (an experienced singer can prolonge this moment of singing without sound for quite a long time and it is something special to experience). Inside we have lots of other structures vibrating, we are not at the zero absolute point so everything in us ocillates,  sometimes vibrating in accordance with something else outside transmitting the oscillation or determined by our specific inside or even a sum of both. A good point to start singing is to just give an internal movement to breath related structures so to have a clear sound coming from our instrument that is generally what is perceived as our voice. The interpreter will make you dream, and have all this incredible effects a voice can have, does not just listen to its vocal folds and big muscles vibrating the note but hears and chooses something more precise perceived inside or outside, and puts the wave starting from this other point of oscillation or its waves to reach it in a summable way so to sum it in his proper voice and so making heard what sometimes we call the invisible that become visible. Truest interpreter will sound on something they feel as something precious or significant or simply with an inexplicable charm vibrating somewhere and just making it being where the wave starts or arrives to give it a voice.