Earlier today while listening to some video game music the question crossed my mind about where the stereotypical 'evil laugh' that comes up so often in music, games, movies, books, and so on comes from. Think this sort of thing, the ol 'muahahahaha'. Where did it first appear? Are there instances of old literature that describe such a laugh, or is it the product of more modern times when audio recording became more prevalent? These days it's practically everywhere in all forms of popular culture and it's hard to imagine what iconic thing denoted that a certain individual was the 'bad guy' before the evil laugh. That being said, as a follow up question of sorts, what was used commonly to denote the 'bad guy' before the occurrence of the evil laugh we know today?
Cool question BTW. There are quite a few instances of it being used in older literature. The best firm "proof" goes back to the 1800s when a few different journals had some short stories with the use of this laugh. Most notably, The Living Age. There are references to maniacal and sardonic laughter before that in some old letters that we have.
The actual noise and sound clips you are referencing became a hit during the early 20th century with the rise of radio drama. Radio programs like "The Shadow" started using it to set the mood. Hope that helps.
Before television/film there was theatre, and there are several instances of something like "the evil laugh" showing up in plays/operas. TVtropes has a good list of examples.
In general the "Evil Laugh" is effective because it shows two things about the antagonist - that they are overconfident (thus making the hero seem like the bigger underdog) and that they are sadistic (they enjoy violence as opposed to seeing it as a necessary means to an end). And it is easy to come up with ways antagonists in stories can display both of these things without a laugh - (adding insult to injury , mocking the hero for example). Other common ways of "creating a bad guy" would be to show them doing something bad for no apparent gain (like kicking a dog). And of course anything that makes them seem more foreign, physically or culturally, from the audience would make them less relatable and less likable so an author could play those up to make them seem untrustworthy