His music can seem simple to play but works must take and enormous amount of concentration to execute properly.
You're not wrong. I had to play in an ensemble performing the second movement of his Electronic Counterpoint compositions. If I remember correctly, each guitar had to play a 3 bar loop with each bar having a different time signature. Some people were required to come in on weird off-beats too. In total I think there were around 13 guitarists, including 2 bassists. Those damn bassists messed it up when we did the final performance. The conductor did not look too impressed.