I’m not sure if this applies to all missions, but as I started the first mission of the RoC human campaign the generic human music plays during the cutscene. You can look up on YouTube what the music is supposed to be like. I am using the WC3 only music option.
I’m having the same issue but its even worse.
When I play campaign (RoC or TFT), and load the game while I play, I get 2nd music playing simultaneously. Furthermore when I complete campaign and the cutscene is being played I’ve got this 2nd bugged music still playing in the cutscene. It’s even still playing when I quit to Main Menu. When I quit the game completly it goes back to normal, but only 'till I play campaign mission and load the game again - I get the same bug.