Ben Johnston is an American composer internationally known for his work with extended just intonation. This is a critical-analytical study of his early compositions, his studies with Harry Partch and John Cage, and his experiments with just intonation, serialism, indeterminacy, jazz, and finally, extended just intonation. Pieces are analyzed and biographical material is included. The main emphasis of the text, however, is on examining Johnston's research about tuning and scalar theory as it relates to just intonation. For a long time Johnston worked in isolation; few people understood why someone would want to change the standard pitch system. But gradually, as his music began to be heard, especially his string quartets, performers and audiences experienced for themselves the kind of clarity and beauty that is possible with just intonation. This book is written for readers of varying musical backgrounds. Thos interested in studying and performing Johnston's music will find the book helpful in understanding his notational system and learning how to listen for just intervals. Many examples and figures document the musical analyses, which explain his compositional techniques. With a foreword by John Cage, a catalog and discography of Johnston's music, and a bibliography of the composer's writings.