The 1920’s saw major developments in popular music in the United States. Some of the most important were technological: the establishment of commercial radio stations and the development of the public-address system, the sound track for film, and the electrical recording process used for producing phonograph records. All used the microphone and the sound amplifier, with significant impact on the nature of orchestration and popular vocal style, and consequently on the ideas of performers, arrangers, and even songwriters. All tended to broaden the audience for popular music—in a sense to nationalize it—but at the same time they tended to make it a more passive one, an audience of listeners rather than participants. This process tended to heighten the importance of professionalism and sophistication among both performers and arrangers; it also tended to increase commercialism in the transmission (the “distribution”) of popular music to its audience. Thus, the era of the American popular music industry was born—an inevitable result of the electronic age’s “mass media” (though the term was not yet coined). New York City was the center of the popular music industry during the 1920’s: it had Broadway and Schubert Alley, center of the American popular musical theater, and it had Tin Pan Alley, center of the songwriting business and the still-powerful sheet music publishers. The recording studios and radio networks were also based in New York. In addition, recordings and radio opened up new possibilities for a striking new development. They made available kinds of popular music heard previously only in limited geographical areas or by specific ethnic and social groups—especially the blues, gospel songs, and jazz of African Americans and the traditional music of the southern Appalachian Mountains and other rural areas of the southern and western United States. The latter music was not to affect the mainstream of American popular music until much later, but the former influenced American popular music of the 1920’s in many ways. In fact, novelist F. Scott Fitzgerald could even call the era “The Jazz Age”—which reflected the inroads of African American musical influence on the nation at large.