The "underground" music of the first half of the decade marks the popularization and commercialization of many styles of music in their original (or close to original) forms such as jazz, blues and country.
While Hollywood and mainstream popular music were peddling confidence, optimism and diversion to a public weary with the drudgery of the Depression, underground musicians were struggling to keep open the avenues that offered them the opportunity to make meaning in American culture. Many early forms of important underground expressions had entered the lexicon of American popular music during the twenties and early thirties. The classic blues of female African American vocalists from the vaudeville tradition, the rural blues, the country blues and the small group Hokum style were all documented and marketed before the Depression.
When swing more or less dominated the mainstream in the mid-thirties, important developments were happening in the underground that would shape the future of American musical forms and have an impact that would last in modern American music of the present day. Jazz of the thirties, for example, hinted towards new styles of bebop and cool jazz under the direction of such artists as Duke Ellington, Count Basie, Louis Armstrong, Fletcher Henderson, Lionel Hampton, Lester Young, and many others. The blues and jazz of African American musicians would fuse stylistically into rhythm and blues through the efforts of such artists as Billie Holiday, Ella Fitzgerald, and Cleo Brown.
Artists such as Roy Acuff, Bill Monroe, Bob Wills, and Gene Autry professionalized country music into its modern forms of country, western, and bluegrass. Woodie Guthrie and other artists popularized a new twist on folk music that would become known as the urban folk movement.
The reaffirmation of identity and cultural cross-pollinization of styles that characterized underground music began to interact with the mainstream and influenced the work of chart favorites like the Andrews Sisters and Guy Lombardo. Yet, these many forms of underground music were being appropriated and often sanitized for consumption for the mainstream audience by record producers such as John Hammond and recognized performers like Bing Crosby and Benny Goodman.