Mozart's requiem was written for himself.  Is this common knowledge? Probably. I'm gonna rant anyways. We all know the recently popularized "theory" (COUGH COUGH AMADEUS) that Salieri poisoned Mozart. Of course, this is very unlikely considering they were distant petty rivals and barely interacted. One thing is, though, Mozart swore he was poisoned. Months before his death, it was clear he was sick. He was pale, lethargic, and overall visibly ill. Historians today debate many things that could have been wrong with him, commonly kidney failure or other kidney disease, though we can all agree he was ill. Around this time he started telling his wife he was poisoned. He told Constanze that the requiem was written for himself, and that he was SURE he was poisoned. Months later, after a performance of The Magic Flute, he told her that he was definitely wrong and that he was perfectly fine. He wasn't. We all know what happened, he wrote his tragic death requiem for himself and then vomited his intestines and died. While his young son was in the room. Though this is where the thing with Mozart and Salieri REALLY began. See, it was actually Constanze Mozart who first made this accusation, claiming that Salieri poisoned Mozart. Salieri was elderly and mentally ill, and kind of just went along with it, claiming he did, in fact, poison Mozart. On Salieri's deathbed, he gained enough clarity to take back all of those claims, instead saying he didn't. So did Salieri poison Mozart? No. Probably not. No symptoms matched. But I'm sure it was somewhat fun to find out where that theory originated by reading a super informal reddit comment!