Learning to breathe in the right way at the right time is an essential part of piano technique. Some pianists may have a natural ability to do so while others need detailed guidance. Many pianists, without being aware, tend to hold their breath while practicing - especially during difficult passages. Pianists who do not breathe properly may find themselves completely exhausted after a short practice session or performance. Pianists who are able to control and command their breath in the correct way tend to have more relaxing practice sessions and performances, as well as higher energy levels during and after practice or performance.
Jodi Russell, B.M.,M.M.,NCTM