Roots music
Roots music developed its most expressive and varied forms in the first three decades of the 20th century. The Great Depression and the Dust Bowl were extremely important in disseminating these musical styles to the rest of the country, as Delta blues masters, itinerant honky tonk singers, Cajun musicians spread to cities like Chicago, Los Angeles, and New York. The growth of the recording industry in the same period was also important; higher potential profits from music placed pressure on artists, songwriters, and label executives to replicate previous hit songs. This meant that musical fads, such as Hawaiian slack-key guitar, never died out completely, since a broad range of rhythms, instruments, and vocal stylings were incorporated into disparate popular genres.