No game music on 2 player realm

I created a realm, but when I enter before my friend, music won't play, but he still can hear the music. But if he is on the realm, and I enter, music will play. But I mostly play alone these days, so I've being playing without music for weeks.

Discs music works fine, but if I go anywher, I just hear ambience sounds (water, lava, rails...)

 

Thanks