The motivation for the research project leading to this book is the result of 40 years of experience as a classical singer and a teacher of young classical singers. During these years, a growing interest and need for more specific knowledge concerning muscle usage in singing gradually developed. Even if opinions on how to use muscles vary considerably among singers and singing teachers, they seem to agree on one thing: muscles utilized shall be used as economical as possible. What is lacking, however, is a nuanced understanding of what is meant by economical. This book is an attempt to approach this issue. New research findings on the use of breathing muscles are presented. Abdominal, chest, shoulder and neck muscles are investigated, as well as the movement of the diaphragm and the thorax. All findings are presented in text and illustrated in figures, and the interpretation and pedagogical applicability of the results are discussed.