Autohotkey script to mute the current application by pressing F1. This will ONLY mute the application that is in focus, leaving all background applications still audible.
F1 is no good for you? Keybinding can be changed here
To do this, you'll need to download a copy of Autohotkey yourself, download source files, make the neccesary changes, and then compile them. Or ask a friend who knows these kinda things to do it for you.
Alt = '!'
Control = '^'
Shift = '+'
+F1 then becomes Shift+F1 on keyboard.
^m then becomes Control+M on keyboard.
^+m then becomes control + shift + m on keyboard
It is possible to stack multiple keybinds on top of each other to all perform the same action.