From Encyclopedia of the Pivot System

7. What are the three primary playing factors?
The three primary playing factors are: first, the embouchureformation (the lips, the mouthcorners, the cheeks and the entire facial area involved while playing); second, the tongue and its manipulation (the tongue-arch, the tongue-level, and the length of the tongue backstroke): and third, the breathing (the diaphragm and abdominal regions, the ribs, the shoulder blades, the lungs, and the throat).

8. Which one of the three primary playing factors is considered the most important?
All three primary playing factors (the embouchure formation, the tongue manipulation, and the breathing) vary in relative importance at different stages throughout the student's career. Therefore, no one factor may be considered the most important except in relation to the student's degree of development.

Most of our finest present-day performers agree that they consider correct breathing the most important physical playing factor. This statement is quite true but only after the player has arrived at his final stages of playing perfection. Some of these fine artists have had the good fortune of playing correctly for such a long period of time that they are inclined to forget some of the difficulties that they too had encountered before they reached their present high playing level. Much like riding a bicycle, you may have been riding for so many years that you have completely forgotten the difficulties encountered and the number of times that you fell off before your sense of equilibrium took hold and made you a rider.

If a very fine oboist selects an excellent instrument but uses a defective reed, the results will suffer regardless of whether his breathing is correct or incorrect. The same holds true in brass playing! It is logical to assume that the embouchure formation (the lips, the mouthcorners, the cheeks, and the entire facial area involved while playing) and the tongue manipulation (the tongue-arch, the tongue-level, and the length of the tongue backstroke) must not only be functioning properly as separate and independent factors, but must definitely be synchronized with the breathing factor (the diaphragm, the abdominal regions, the ribs, the shoulder blades, the lungs, and the throat) before any relaxed playing perfection can possibly take place. For example: if a performers playing difficulty is analyzed and traced to a faulty embouchure formation, the error must certainly be corrected and the tongue and breathing factors be given ample time to compensate themselves the the new and slightly different blowing resistance of the "adjusted embouchure" before coordination of the primary playing factors can be obtained. (Page 4)