The specialized book "On the Effect of Keys in Music" offers a well-founded introduction to the fascinating world of keys and their emotional impact. Written by Sigismund von Gleich, it illuminates the characteristic features of the twelve keys and their connection to the zodiac. The text summarizes current research findings and includes a special section on minor keys, authored by Clemens von Gleich. With a clear and concise writing style, the book is aimed at anyone looking to develop a deeper understanding of the musical power of keys. It is a valuable work for music lovers, students, and professionals engaged in the theory and practice of music.