When we sing, this mental nervous energy is the underpinning of our ability to have muscles and air moving to create sound. As a singer, we feel this energy like an excitement we can gather up and channel. Makes me think of shaking up a can of soda and popping the top!
We can be more energetic or less energetic, depending on the mood of the song. With good training, our muscles will respond automatically, bringing the song to life and reflecting our emotions through sound waves inspired by our imagination and electrified with our life energy.