The first music made entirely from recorded sound. Schaeffer captured trains, spinning tops, canal boats, and iron lids, then cut and manipulated them in the studio at Radiodiffusion Française. He called it musique concrète, where the sound itself was the raw material, not a notation of it.

A single grey rectangle. Amplitude determines luminosity. The directness mirrors Schaeffer's method: no abstraction, no mediation, only the material of sound itself.