Is Honesty The Best Way?
While there are a lot of things that are far worse than having a neighbor who sings excessively loud (and bad), the person suffering is not something that should be invalidated. If that is among the things that grind your gears, then you should perhaps consider yourself lucky. Some people might find it hard to confront the irritating neighbor because it might incite a much bigger conflict. Has there been an existing misunderstanding between both parties? Now might be the time to resolve them.
However, in the following scenario, one neighbor has had enough of the irritating noise that penetrates their walls. The neighbor has exclaimed disgust by sticking a note that says, “YOU SING HORRIBLY.” If the problem continues, then an investment in noise-canceling headphones might be a good idea!