Musique concrète (, meaning "concrete music") is a genre of electroacoustic music that is made in part from acousmatic sound, or sound without an apparent originating cause. It can feature sounds derived from recordings of musical instruments, the human voice, and the natural environment as well as those created using synthesizers and computer-based digital signal processing. 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.