When I was 13 I so wanted to play hooky and go and hear Répons, by Pierre Boulez, but it was going to be difficult, so I listened to it on the radio and recorded it, and listened and listened and listened over and over and over again.
It was at the Proms. There was a regular brass and string orchestra in a square in the middle of the room. Around them were percussive instrument players such as piano, cimbalom, harp etc. Those ones were modulated using all kinds of effects that in those days were very complex: ring modulation, delay, phasing, and computer generated patterns. The audience sat in the outer ring around that.
After about 6 minutes the percussive instruments come in. It's like a door opens in the floor and you realize you are falling out of a plane...
I was smitten.
You know what it's like? It's like glimpsing another dimension. Like when Brand looks out of the window in the wormhole in Interstellar and sees Them, 5-dimensional beings distorting spacetime.
Pierre Boulez RIP.