Because the underwater music is not stop playing when you already on surface
And also, mojang made an error: they placed vanilla_music folder into the music folder. This is the reason why music didn't play when you install the update. To fix that, find in resource_pack folder music folder and copy vanilla_music back to resource_pack folder.
Владислав Архипов
Well, already updated, but still need fixes.
Because the underwater music is not stop playing when you already on surface
And also, mojang made an error: they placed vanilla_music folder into the music folder. This is the reason why music didn't play when you install the update. To fix that, find in resource_pack folder music folder and copy vanilla_music back to resource_pack folder.
Have fun!