I had been working as a roadie and a sound tech for one rock band or another for about ten years, when I finally had my one brilliant idea in life.
I used to do everything from setting up the lights to tuning the guitars and checking the speaker levels.
Then one night we were working for a Black Sabbath reunion show, and at this point in life all of these guys were very old. Have you seen Ozzy lately, he looks like a mummy! Anyway, the boys in the band got overheated during their show, and I saw one of the roadies drag a small air conditioner out on the stage and set it next to the drum kit. I realized that these stages could have hidden ductwork built into them, so the musicians could have air vents to keep them cool under the hot stage lights. That was it, my one brilliant idea I ever had, so I had to make it count. I spent a few months working with my Uncle Mike, who taught me how to work with sheet metal and make air ductwork. Once I had the skills I pitched my idea to the band manager, who hired me on the spot to become the HVAC tech for the stage crew. I was regularly loaned out to other bands so I could modify their stage setup to accommodate air conditioning systems. That was a few years ago, and at this point everyone uses my idea, and having A/C built into the stage is something all major bands do.