Going off-key has always been considered a bad thing: letting people down at a crucial moment, being given a chance and still failing to deliver, dragging your companions down with you, and so on. Here's a specific example:
A group of students agreed to climb over the school wall and sneak out. When it was the last person's turn, he lost his grip and slid down the wall. It wasn't very high, but the fall hurt. The commotion alerted a teacher, who caught him and all his friends. Then the teacher made them climb over the wall again, but the last person still couldn't make it...
Hahahaha, I'm dying of laughter. This story has kept me amused for years, and even now, thinking about it still makes me laugh.
I have to say, watching other people go off-key is hilarious. As a professional fun-seeker, I've packed this book with stories of people going off-key. I hope they bring you joy.