One might speak of the blues as a single song form or genre, because virtually all blues share certain qualities of lyric and music, or at least share a sentiment that is, in some sense, “blue.” Yet within any genre there are subgenres, and this is certainly true of the blues. As I make no claim that this study describes all blues in all its forms and in all its contexts, I am obliged to define the corpus of those songs that I have included in my analysis and on which I base my theory of formulaic composition.