Following his work with Studio d'Essai at Radiodiffusion Franaise (RDF), during the early 1940s, Pierre Schaeffer is credited with originating the theory and practice of musique concrte. In the late 1940s, experiments in sound-based composition using shellac record players were first conducted by Schaeffer. In 1950, the techniques of musique concrete were expanded when magnetic tape machines were used to explore sound manipulation practices such as speed variation (pitch shift) and tape splicing.[36][37]