Harry Partch's tuning system is an important contribution to tuning theory, and his music is original and significant. Part One of this study presents a brief biography of Partch, a discussion of his musical aesthetics (Monophony and Corporeality), and a technical summary of his tuning system. These elements are placed in historical perspective. Part Two presents a comprehensive analysis of "And on the Seventh Day Petals Fell on Petaluma," discussing the organization of formal, textural, rhythmic, linear, and tonal elements in the thirty-four "verses" of the work. Part Two concludes by showing how large-scale structure in the work is achieved through an overlay process.