My book Yesterdays was not written as an overview of popular music but as a narrative history of the musical and social origins of a single genre, popular song, which I defined as follows:

• written for, and most often performed by, a single voice or a small group of singers, accompanied by either a single chord-playing instrument or some type of band, ensemble, or small orchestra;

• usually first performed and popularized in some form of secular stage entertainment, and afterwards consumed (performed or listened to) in the home;

• composed and marketed with the goal of financial gain;

• Designed to be performed by and listened to by persons of limited musical training and ability; and

• produced and disseminated in physical form – as sheet music in its early history, and in various forms of mechanical reproduction in the twentieth century.

There was no intent of privileging this genre over others. As I pointed out myself, this definition “excludes the music of William Billings, which is for vocal ensemble; Child ballads and other traditional Anglo-American songs, which were transmitted in oral tradition; the band music of John Philip Sousa and the ragtime music of Scott Joplin and others, which is instrumental; all church music, even that for solo voice; most jazz, which is instrumental.” But I emphasized that “the exclusion of these and other kinds of music from this book – except as they exert direct influence on popular song – does not imply that they are less interesting or important than the music dealt with here, merely that they are something different.”