Japanese FM radio is now considered as a music media which is distinct from other broadcast media such as AM radio. However, FM radio was originally planned as an educational media. Many political and cultural factors influenced the process of the formation of FM radio as a music media. During this process, sound, not music, was an essential factor. This article discusses the functions given to FM radio with a historical description on how the main role of FM radio changed from educational broadcasting, during the end of the 1950s when its experimental broadcasting started, to music broadcasting in the early 1970s when its formal broadcasting began.