In Theory: The Trumpet is a supplementary text, which uniquely parallels a basic elementary music theory curriculum. The method provides trumpet students the opportunity to apply to trumpet many concepts of elementary theory, and is presented in a concise manner congruent to an introductory theory course. Concepts presented in this book may benefit high school and college students currently taking an elementary theory course. Furthermore, this method serves as a valuable resource for educators who wish to provide students with supplemental applied lesson materials.