When playing Minecraft and switching between worlds, after a while two music tracks play over each other. This only happens when switching between worlds.It has also happened to me just on the main menu. there are 2 others similar to this but this is in 1.9 not a snapshot or 1.8

Steps to Reproduce:
1. open up a Minecraft world in 1.9
2. wait for music to start
3. exit world
4. wait for a music track to start
5. open up a world again
6. Two music tracks should start to play

has also happened this way:
1. wait on main menu for 10-15 minutes