Sound collage, aka musique concrete? Pierre Schaeffer in the late 1940's, Beatles in the late 1960's.
Of course there is always Les Paul messing with tape speed in 1950's pop music.
Synthesizers? Milton Babbitt in the early 1960's, The Byrds in the late 1960's.
Turntables as instruments? Paul Hindemith and John Cage in the 1930's, DJ Kool Herc and Grandwizard Theodore in the late 1970's.
I could go on. The mainstream music audience gets their ears adjusted somehow.