That's what it says in bgt/help/[english]postinstall.htm about BGTMusic:
Install none: No Baldur’s Gate and Tales of the Sword Coast music will be heard in the corresponding portion of the game. The music heard during Baldur’s Gate and Tales of the Sword Coast will sound inappropriate.
So BGTMusic should be installed.
TobEx replaces BGTMusic patch from this component:
Full Baldur's Gate/Shadows of Amn/Throne of Bhaal Music (WARNING: patches BGMain.exe)
Corresponding code from Setup-BGTMusic.tp2 you can see here.
Install a minimal version with BGTMusic patch from latest Fixpack and with latest version of WeiDU, and music plays in the problem location is correct. The rest locations are not tested.