This chapter focuses on how the concept of folk music played out more specifically in Eastern Europe. Most studies of European musics posit three basic categories of music: folk, popular, and classical. The musical sounds of folk music were always of interest, however, and the ethnographic study of the music was greatly enhanced by the invention of sound-recording technologies in the 1880s. The chapter mentions a few song collectors who contributed to the understanding of what constitutes folk music in Eastern Europe. Ethnomusicological and musical-folklore literatures offer many overviews of folk-music sound in Eastern Europe. The chapter sketches some organizing structures such as religion, life ways, musical instruments and song forms of ethnographic fact. Folk music generated different meanings and served different ideologies in Eastern Europe from other parts of Europe. This may have been particularly true among the Slavic peoples.