(From: http://www.soundart.zone/2016/11/23/pie ... uits-1948/)By 1948 he had learned how to lock-groove records, meaning that instead of a disc consisting of a spiral groove that went toward the center of the disc, there was a single circular groove (or a series of circular grooves) that could play a continuous loop. He became interested in studying the nature of natural sounds, creating recordings of percussion instruments struck in different ways, and editing recordings of bells. He discovered that, in addition to timbre, sounds could be classified by their change in volume over time (the envelope), particularly by the initial rise in volume (attack) and overall volume shape following the attack (sustain-decay).
https://www.youtube.com/watch?v=CTf0yE15zzI
https://en.wikipedia.org/wiki/Cinq_%C3% ... _de_bruits
