I have the same issue on my normal world on PlayStation. I use the norse mythology texture pack. The awesome soundtrack worked when I started to play the world. After a few hours of progress in the world it stopped to play. The standard music plays now instead of the norse myth soundtrack. I tried to active and deactivate the texture pack and to restart it but nothing worked.
Bombenprank
I have the same issue on my normal world on PlayStation. I use the norse mythology texture pack. The awesome soundtrack worked when I started to play the world. After a few hours of progress in the world it stopped to play. The standard music plays now instead of the norse myth soundtrack. I tried to active and deactivate the texture pack and to restart it but nothing worked.