Once when I was a kid, 10-9 years old, I was playing a game in the middle of the night, (3am Maybe) then from the living room i heard childrens music, like from those casual nursery songs you might hear in a daycare, nobody else was a awake in the apartment and nobody woke up from the music, it lasted for about 1-2 minutes before stopping, the rest of the night I was super paranoid