Is there any way to disable the BGM when getting FR pills?

Just a little bit annoying when crafting since it covers the sounds of SI.

 

Actually I've tried to find that sound and found it's in ~\left4dead2\sound\music\safe . However, after I removed the files in that folder the BGM still played when getting the pills. So I think maybe there's a particular folder containing the same music files but named maybe something like "FR pill" or "FR" I don't know, and the fact is there're no folders like these names and there're too many folders which makes me think it's a waste of time to check them one by one.

And that's what makes me post here to see if anyone know that folder or if there's any other way :unsure:

 

Yes you are right.
First I removed the files in that folder, and after gettling the pills everything came to be infinitely mute except characters' talking until next round.
Then I put a fake file with 1sec length into that folder, then after getting the pills everything still came to be mute except characters' talking, but after the same time as the length of the original file the sounds came back.
It seems that after getting the pills, the system will first disable all the sounds except the characters' to prepare, then search for the files in that folder to play. What I've done is just to change the music to be played but can't intervene that sounds disabling process...
Anyway it's better than listen to that music over and over again.
Many thanks