Getting all keys to work.
Install xbindkeys with Sourcery or slapt-src.
while the blank window is open, press the key which you wish to assign a command (Decrease volume).
copy the three lines to ~/.xbindkeysrc and replace "(Scheme function)" with the command you wish to perform.
In the above example "amixer sset Master 2- unmute"
"amixer sset Master 2- unmute"
Once you're done configuring your keys create a autostart of xbindkeys.
If you are running XFCE start xfce4-session-settings and under autostart add xbindkeys.