In the introduction to “Corners” Allan Colin writes: “If you glance through these pages, do not be fooled by the diatonically simple configuration of notes. The challenge here lies in doing these exercises from top to bottom exactly as specified. The goal is to strengthen weak corner muscles which plague many trumpet players. In your effort to accomplish this it is imperative not to overdo it. As with any practice session where you are trying to straighten out a problem, the “warm-up” and “warm-down” exercises are essential The warm-up and warm-down exercises here are geared to prepare you for and relax you from this short but strenuous work-out.” This book is broken up into four sections, including articulations, corner “close-ups”, chromatics, and warm downs, each with an explanation of how to proceed to get the strongest embouchure possible.
