I believe he is drawing a parallel between a tone of pure joy and the most depressing despair.
Schedule reminders about meeting times and locations for classes, club meetings, sports practices, and more.
Answer:
what story are you talking about?
When doing something like this, some find it useful to annotate the text by putting in notes and explanations of what is being said.
(Like pastors at a church when giving the message, or a comedian needing to remember some little things)
It basically just helps the reader not forget side notes or little things that can make the others either more entertained or more helpful.