The term "vocal control" in singing refers to the control of volume of the sound that comes out of the singer's mouth. Most singers don't really know how to do this. There are some singers who are not even fully aware that the volume of their voice is too loud. One of the causes of this problem is the possibility of a hearing deficiency.
You will experience this when you put a set of headphones on your ears and then speak at the same time, you will be told afterwards that you spoke louder than usual. You become too conscious that you cannot be heard by the person you're talking to, so you tend to speak louder. But the actual reason is because you yourself can hardly hear your own voice.
One of the ways how to control the volume is to regulate your airflow when you sing. My breathing exercise called "Blow the Candle" is a good exercise to achieve this objective. By regulating the airflow, you are also reducing the volume of your voice.
In this lesson, you will be able to learn how to control your voice by regulating your airflow through proper breathing exercise.