As we have referenced in other little blurbs, air is important. It is for energy as well as for literally moving through the cords to become shaped sound.
Some folks, myself included, have tried to control the air; thinking it was the expenditure of air that determined a lot of what singing was about. I remember that I used to go to the gym and workout on a machine to try to strengthen my internal and external intercostal muscles. Oh, for different reasons, if only I had worked on my six-pack abs that hard!
I figured that if only I could get the breath under control, then place the tone in this certain spot—bam—singing solved in 2 easy steps. Unfortunately, I discovered that singing is a much more dynamic process involving the balance between two main muscle groups drawing the vocal cords into some sort of configuration, as well as air movement.
What is more is that this air movement is not to be controlled, as localized direct abdominal control introduces unnecessary tension and rigidity. Instead, the mechanics work quite differently:
Therefore, instead of attempting control of air, the singer can focus on how the air is moving in and out as a part of tone and for emotional content!
Keep the air moving, don't inhibit, and trust your vocal cord adjustment to let out what needs to exit!