Right now there is no way for you to turn off the Loading Screen Music other than completely turning of UI sounds. This can be annoying when you still want UI sounds but not Loading Screen Music.

I know a lot of people who have their UI Sounds turned off completely, because they want to listen to their own music and not the Loading Screen.

Consider adding a toggle and volume slider for the Loading Screen Music, it could be called something like and be put in the General Settings section of the User Interface Category of the Main Menu Settings Tab.

It would allow users to separately turn down the Loading Screen Music Volume from the rest of the UI if they for example want to listen to their own music.

Here you can see how I could imagine this looking: