A theory of the structure of rock music is presented, addressing aspects such as tonality/key, harmony, rhythm/meter, melody, phrase structure, timbre/instrumentation, form, and emotional expression. The book brings together ideas from the author’s previous articles but also contains substantial new material. Rock is defined broadly (as it often is) to include a wide range of late twentieth-century Anglo-American popular styles, including 1950s rock & roll, Motown, soul, “British invasion” rock, soft rock, heavy metal, disco, new wave, and alternative rock. The study largely employs the informal, intuitive methods of conventional music theory and analysis, but it is also informed by corpus data. An important component of the theory is a representation of pitches—the “line of fifths”—that sheds light on issues such as stylistic distinctions within rock, effects of surprise, and emotion. The theory also entails a model of expression with three dimensions, representing valence, energy, and tension; this proves to be a powerful tool for tracing shifts in expressive effect within songs. The theory features novel approaches to issues such as cadences, melodic-harmonic coordination, the handling of sectional boundaries, and the classification of formal types. The final two chapters present analyses of six songs and a broader consideration of rock in its historical and stylistic context.