I think there may already be a flag in said scene's script file. Without looking the quickest route to accomplishing disabling the auto-read is to do an if statement for a flag check right in the beginning of the file which sets the auto-read on or off. You can just make a copy of the bgm with a different name and .sli file and set the bgm within the if else statement.... In theory I'm too lazy to look.And this is if you even consider the kag scripts to be 'programming'