The All-Important Rule of Performance: Never play the riff of the tune you are getting ready to play during soundcheck. The rule applies to rock as well as classical concerts. I find it fascinating what musicians choose to play instead during this time.
My favorite part of a concert event is generally not the performance at all, but the ambience before, after and in-between. Especially shows with a live orchestra that warms up on stage or in the pit. The resulting sound is usually an atonal mass of sound with no structure, even to aleatoric 20th Century standards.
One of my band directors was quite aware of and must have despised this dissonant bliss, and always instructed the wind symphony to warm up only in a set concert key, limiting us to a more “pleasing” 12 note selection of the Ionian mode. I’d consistently make a point to discretely produce the occasional tritone or minor second to see if he was paying attention. He was.
I have encountered a true gem while scrutinizing the interwebs.
http://www.delaurenti.net/music.htm
It is a binaural recording, so please remember to use headphones!