teachers talk about the diaphragm. It is a large muscle that makes a horizontal dome underneath the lungs, at about the level of the lowest ribs on the outside of the body, curving upward in the center. The dome flattens out when you take a deep breath. Deep breaths are not the “suck in the tummy” type, but expanding low in the body. Release the muscles that pull in against the stomach so that it can squish outward and the diaphragm can descend. A rigid abdomen will not allow the diaphragm to descend and the lungs will only fill partway. Remember the lungs fill downward, and filled halfway means the air is in the top half. That will cause a lot of tension in the shoulder region, which affects the voice
adversely.In addition, the lowest ribs on both sides can expand outward. This may be hard to feel, at first. What’s even harder is getting the ribs to stay in that outward position to avoid pulling in as you sing.
When asked to take a deep breath, many people lift their shoulders and clavicle. This type of breathing will get the runner a little more air, but involves a lot of work from the muscles of the neck and shoulders, which a singer cannot afford. It’s also not a breath that can be controlled very well.
When it comes to breathing, there are many different schools of thought, and each one seems to work for certain people. Also, the sensations may differ from one person to another, so my explanation may not work for you. However, the majority of voice teachers seem to agree that the general feeling on inhalation ought to be fullness just above the waist. Then sing with a slight pressure inward at a point just above the belly but above the belly button, without collapsing. The ribs want to pull back to their old lazy position, but should be kept wide, while the abdomen area resists squeezing too much toward the
backbone. It should feel like you’re keeping the expansion that you achieved when you took the air in.
To see an animated picture of the breathing process,