Strange "Death" Music Playing at Random

I think I know what sound this is since I have been trying to figure this sound out for *years". It's not a mood notification, since there are plenty of YouTube videos about those (not to mention my two Sims aren't changing moods), and after reading this post -noticing that it happened to the OP every day at 6:00- I'm wondering if he was playing in the winter and that was when it was sunset. Because I've noticed in my current game, which is currently in summer, that short sad guitar (in solfege terms it would be Mi Mi Mi Re Mi Fa if that helps) occurs every night at 9:00. Which would be appropriate for summer -- at least where I'm from. I have searched, but I can't seem to find the answer anywhere. In fact, this post, which I just came across today, is the first time I've seen anybody mention it! I'm about to random Tweet at a SimGuru, but atm they've got bigger fires they're trying to put out...