This is a short thread...I did not realize. I should look up and read.
Xenakis is jaw dropping. Mind blowing is more apt. The first piece that I got, that led me to the others was the piece for violin and piano, Dikhthas. Wow, what a piece! And then really any of the large orchestral works...Tracées is probably the longest, most spellbinding, jaw dropping, mind blowing 6 minutes in the history of music. It's the one piece I'd love to conduct more than any other, if I was a conductor...just to start a subscription concert out with Tracées, no explanations and no apologies...to have people trapped in the room with that massive, unrelenting, unbelievable sound for six minutes. It is an actual dream of mine! And then there's the impossible trombone piece, Troorkh

Xenakis is without a doubt the most jaw dropping composer there is.
(...a 60 note chord in the strings....

)