What Is Diaphragmatic Breathing?
Belly breathing, abdominal breathing — the foundation of breath support
The diaphragm is a large, dome-shaped muscle that sits underneath the lungs, separating the chest from the abdomen. When it contracts, it flattens and drops downward, which pulls air deep into the lungs and pushes the belly and lower ribs outward to make room. As the breath deepens, the intercostal muscles, the muscles of the abdomen, oblique muscles and the lower back all expand outward to create more room. As the diaphragm relaxes and the aforementioned muscles support the airstream, the diaphragm domes back up and the air is pushed out. This is diaphragmatic breathing — also called belly breathing, abdominal breathing or deep breathing — and it is the way we are designed to breathe. Watch a sleeping baby or a relaxed dog: the belly rises and falls, the chest barely moves.
Most adults, though, have drifted into shallow chest breathing — quick, high breaths that fill only the top of the lungs and lift the shoulders. It is enough to sit at a desk, but it is hopeless for playing a wind instrument, where you need a large reservoir of air and precise control over how slowly you release it. The single biggest improvement most players can make is to relearn how to breathe low.
A practical caution about language: many teachers say "breathe from your diaphragm" or "push with your diaphragm", but the diaphragm is an involuntary muscle most people cannot consciously feel or command. It is far more useful to think about the visible, controllable result — the belly and lower ribs expanding outward on the in-breath. If you make the belly move, the diaphragm is doing its job automatically. Don't try to control the muscle; control the motion you can actually feel.