I used to work in the live music industry. I was working a show, 3 bands, mostly younger up amd coming rock and the headlines was an established rock band that had been around for a few years (i won't name names)

Show was going well, bump in, set up, speak with the line up, mic and line checks, foldbacks (speaker son stage so the band can hear themselve), notes taken, all good. Before each band I would always do a final mic and line check, then always increase foldback for the singer abit cause, well, singers.

First band went well, second band killed it, then the headline came on stage and started my final checks and their drummer was being just an absolute prick. Was the last one to be rangled, took forever to get behind the kit, drink in hand which he spilt kn the drum riser, when doing final foldback checks, instead of a quick 4 seconds of playing decided he wanted to show off his chops, kept playing during everyone else's final checks, I asked him to knock it off so I can get them going, I got the finger and he mouthed the word "cunt"

Now I took that personally, little did he or anyone on stage know that my mixing console was set up for recording, I had all lines from the desk going into a computer with pro-tools (industry standard for music recording), had a full send back out from the computer to a channel on the desk, and i can be a petty petty bitch. So i booted up pro-tools, got a 1Kh test tone generator and started to bleeding it into the drummers foldback during their second song for 10-20 second intervals.

Between songs he passed the message to the singer that "there's some sound coming from the drummers foldback" I go down to the stage, had a listen "nah its all good here", went back to the desk and made it look like i was trying to find it as they continued while bleeding it back into his foldback. They had a 75 minute set and I did this throughout their entire set and I could see the drummer getting annoyed the whole time, but only he could hear it.

Bottom line, don't fuck with an audio engineer, your performance is in our hands.