? They do that in my Japanese town of Kumagaya but that is for the kids to go home because it is getting dark. It changes to 4 or 5pm depending on the time of year. Are you sure that music is to remind adults that it is time to go home?
I dunno, they did it in hachioji when I lived there several years back. I remember it being at 6 and I remember my coworkers telling me that was the reason for it but I could be mistaken.