The phrase "popular music revolution" may instantly bring to mind such twentieth-century musical movements as jazz and rock 'n' roll. In Sounds of the Metropolis, however, Derek Scott argues that the first popular music revolution actually occurred in the nineteenth century, illustrating how a distinct group of popular styles first began to assert their independence and values. He explains the popular music revolution as driven by social changes and theincorporation of music into a system of capitalist enterprise, which ultimately resulted in a polarization between musical entertainment (or "commercial" music) and "serious" art. He focuses on the key genres and styles that precipitated musical change at that time, and that continued to have an impact uponpopular music in the next century.