I've been noticing this issue ever since December 27, 2017. In 1.12.1 and 1.12.2, the theme music in my Minecraft game in particular has been overlapping. I would hear about two, or rarely three, of the theme songs overlapped together. Here's how it happened in December 27, 2017,
Opened up Minecraft as usual and the Minecraft menu appears and I click "Singleplayer"
I already created two worlds, the first one is Survival and the other one is Creative.
I decided to make a new Creative world with nothing changed or manipulated.
I spawn in and I walked around the Creative world.
Eventually, I listened to the music and finally notice that two of the theme songs are overlapping.
I did steps 3,4, and 5 again for Survival and Hardcore and the same thing happened.
Because of that day, almost everyday when I open up either Minecraft 1.12.1 or 1.12.2, two of the theme songs eventually start overlapping when I play in a new or old world that I have created in game AND sometimes when I go to the Minecraft menu, the Singleplayer menu, Multiplayer menu, or any other menu in the game, I eventually hear the theme music overlapping.
Does anyone know how to fix this? It has been ANNOYING me even since.