I strongly recommend all wind players read The Structures and Movement of Breathing by Barbara Conable and James Jordan.
Though written as A Primer for Choirs and Choruses, it is invaluable as a guide to any wind player wanting to improve their breathing skills.
It is a concise book, which in a mere 40 or so pages of text and illustrations details the scientific structures and movements of breathing and also lists numerous experiential interpretations of the sensations of the critical process of breathing and support.
The text, often light in tone, manages to convey exacting descriptions of necessary knowledge to educate any performer or teacher without confusion or obfuscating language.
For example, the section on the mouth states:
...the frequent injunction to"breathe low" is confusing to young singers, not because low isn't important- it is terribly important- but because the injunction undervalues and distracts from the equally important higher movement of ribs and diaphragm. Our lungs and diaphragms lie higher in our torsos than any other organs except our hearts, which snuggle between our lungs, just above our highly domed diaphragms. Students ask, "Should we breather high or low?" The answer is yes. We should breathe high, and we should breathe middle, and we should breathe low, across the whole natural range of breathing movement. Fine singing depends on movement choices throughout the entire torso.
Or, in a description differentiating between the Body Map (internal feeling) of the trachea and the esophagus:
The common and very destructive confusion concerning the location of the trachea and esophagus and the function of the pharyngeal muscles is often accompanied by a misunderstanding of sound, which is that sound is a substance, something that a singer may, for instance, "project." Singers with substance fantasies are prone to use the food-moving apparatus to sing. Sound is not a substance; it is merely and purely vibration in air. Singers who comprehend this fact fully move air cleanly in and out through the trachea, using their intercostals and their diaphragms. The esophagus waits there behind the trachea for something good to eat after the rehearsal.
Though the book is based on the ideas of the Alexander Technique, there is no requirement of previous knowledge of the Technique to benefit from the lessons in it.
The illustrations by Tim Phelps are of high quality with just the right amount of helpful detail.