We often identify "high chest" breathing with the sensation of running a hard race. When we are out of breath, we gasp in and out, fast and high. In this state, the shoulders raise and tension abounds. While this is a natural response to physical exertion, in the world of singing, this "clavicular breathing" is highly undesirable.
The primary issue with high chest breathing is that tension is rarely isolated. When the upper chest and shoulders are overworking, that excessive tension translates directly to the vocal apparatus. A tense neck and high larynx make it nearly impossible to achieve a free, resonant tone. To sing well, we must return to a state of calm, relaxed breathing where the shoulders remain settled.
It is important to note that the chest and rib cage will expand during singing—after all, that is where the lungs are located. However, this expansion should not be the result of hurried, frantic tension. Instead, it should be an instinctive function of the body. In a well-trained singer, the subconscious mind calculates exactly how much air is needed for a specific phrase or musical pattern.
Rather than "gasping" for air, the goal is for the conscious mind to give a command, allowing the body to respond reflexively to the stimulus. This is a process of allowing and responding rather than forcing. When you stop the overt effort of "taking" a high breath, you allow the lungs to fill efficiently and deeply, providing the steady support needed for beautiful singing without the interference of shoulder or neck tension.
By moving away from clavicular breathing, you remove one of the biggest roadblocks to vocal freedom. Focus on maintaining a quiet upper body and trusting your reflexive training to provide the air you need. When the breath is calm, the voice can be powerful.