There is no way to turn off the loader screen music. This is a serious problem when loading glitch while on other programs. Please add a mute button or something.
If you hit the escape key, it'll fade out. If you want it muted to begin with, I think you can also turn the music volume down before leaving the game.
Thanks for the hint, but seriously... there is no need for not having a "Mute" icon on the loading screen. That problem has annoyed me many times as well, and it can be easily solved.