You can do a little experiment

So, while the eye controls the movement of the hand as well as most other movement, the ear controls listening.

The ear is an organ of remarkable potential that does not just regulate the listening process but also intervenes in other human activities. We are generally aware of only a few more obvious functions of the ear. Some of its functions—hearing, balance, posture, gait, and the movement of all parts of the body—may seem to be unrelated. There ear is altogether different from other sensory organs: the nose, the skin, or even the eye. Its role is so enormous that we still have much to learn about the way in which it controls our lives. When he decides to put the entire nervous system at the disposal of the ear, man becomes a receiver.

This will to attend is more pronounced when we listen to ourselves speaking than it sometimes is when we listen to others. With singing, the need to attend is even greater. The singer must focus on each sound to give it pitch, color, and inflection while simultaneously adding intention and articulation. This is the essence of control: to make sure that nothing passes without strict verification. However, these are only a few of the parameters that the ear must master in singing. Happily, these controls do become habits, so when the ear is ready all the mechanisms of singing will fall readily into place, leaving the singer free to make music and interpret.

If the right ear is not ready to assume control, no amount of study will produce a dependable enough technique to give the singer the freedom to sing beautifully. We make sense of what the singer transmits to us through experiencing his body sensations reflected in our own. We can tell in our gut when we hear good singing, and our negative reaction is an autonomic self-protective response to bad singing. Most of the time we find singing that is more or less okay and we have a good time at the theater mostly because the music and its effect on us is unmistakable. We immediately know that most of what we have otherwise been hearing has been merely acceptable.

Many years ago, while trying to prove that the right ear is the director, I carried out certain experiments. The simplest one was to saturate the right ear with sound to see what would happen. Any singer who has been subjected to his trial was immediately unable to control his voice. He thought that he was singing easily, as if he had been liberated. What had occurred, however, was that he became freed from his auto-control, just as if he was drunk. It was not a pretty thing to hear.

If you change the way a person listens with the right ear by filtering the sounds you can take away anyone's ability to perform. If you alter zone one (125-750 Hz) he will sing on pitch but with poor quality. Changing how he hears in zone two (750-3000 Hz) he will sing out of tune. Blocking zone three (greater than 3000 Hz) he will sing in tune but devoid of brilliance. You can do a little experiment. If you are right ear dominant and you block your right ear you will note that the sounds seem to be lower in pitch because, by blocking your right ear, you are forced to use the longer route of the left ear and lose some highs along the way. If blocking the right ear does not change the pitch, you have been using the left ear as the dominant. This can be altered by training.

—Alfred A. Tomatis, The Ear and the Voice (1988), translated by Roberta Prada and Pierre Sollier, 2005), p. 21-22