MMISL Blu Ray: Can't hear the vocals during the musical numbers

Hi Everyone:

I received a Blu Ray player for Christmas and a Blu Ray of MMISL. While the dialogue and background music come through fine, the vocals are muted during the singing scenes musical numbers. For example, when Agnes is singing the title song as she walks upstairs in her bloomers after coming back from swimming, you can hear the background music but not her singing. The same with Grandpa picking up the song while in the bathroom, etc.

Has anyone else encountered this issue or have suggestions how to fix it?

I assume it's not the Disc that's defective but some setting on my Blu Ray player. Having just received my player, I'm new to Blu Ray and would appreciate any suggestions on how to correct this issue.

Thanks