Musique concrète is a form of electroacoustic music that is made in part from acousmatic sound. In addition to sounds derived from musical instruments or voices, it may use other sources of sound such as electronic synthesizers or sounds recorded from nature. Also, compositions in this idiom are not restricted to the normal musical rules of melody, harmony, rhythm, metre and so on. Originally contrasted with “pure” elektronische Musik (based solely on the production and manipulation of electronically produced sounds rather than recorded sounds), the theoretical basis of musique concrète as a compositional practice was developed by Pierre Schaeffer, beginning in the early 1940s. The genre emerged out of Europe from the utilization of new music technology developed in the post-Nazi Germany era, following the advance of electroacoustic and acousmatic music.