Breathing for singing is a very relaxed process. When we say you can regulate it, we only mean you ALLOW IT TO HAPPEN so that inhalation and exhalation are done in a way that best suits your musical needs. You do not have to WORK at breathing correctly, unless you have poor posture or a tendency to raise your chest and shoulders and take shallow breaths. Nor do you need to do any special exercises to strengthen your breathing muscles. Your diaphragm, rib muscles, and abdominal muscles are already strong enough for your needs as a singer.

If you maintain good posture when you sing, and are careful not to let your chest “collapse” as you exhale, your diaphragm is able to move freely and be regulated by your abdominal muscles AUTOMATICALLY. There is no need to consciously exert tension in these muscles. If you try to directly control your breathing muscles when you sing, the extra tension in your body will only cause your vocal cords to overtense – to jam up.

Very little air is required to produce a good tone. Even for a loud tone, the amount of air you use need only be enough to SUPPORT the vibration of your vocal folds – no more, no less – so that your tone is produced without any effort or strain. Just as trying to control your breathing muscles directly will cause your vocal cords to jam up, so will using too much air. That’s because, when you sing, your cords are instinctively committed to holding back (or at least trying to hold back) any amount of air you send their way. And, the more air you send them, the tighter your cords have to get to hold it back.

You know you have proper breath support when there is a BALANCE between air and muscle. There will be a mutual and simultaneous coordination of the proper amount of air with the proper adjustment of your vocal cords.

Riggs, Seth, and John Dominick Carratello. Singing for the stars: a complete program for training your voice. Alfred Music Publishing, 1992.