At about 1950, it was no longer self-understood that a sound is a sound, because the idea to compose the sounds themselves came up, as a result we might say, of the historical development […]. And it took a little step to have the idea to compose a single sound, to synthesize a sound. […] One by one, I became aware that a sound is not just a sound […]. The classical instrumentation up to the present day, [which] was the instruments which we can name , has been an art of mixing. Whenever we hear sounds we are changed, we are no longer the same, after having heard certain sounds. And this is the more the case when we hear organized sounds. Organized by another human being, music.
Karlheinz Stockhausen (from the lecture “Four Criteria of Electronic Music” (May 6, 1972)