It could be useful sometimes, so…
Use xev to know the code generate by the button, type xev in a terminal and after a bit of some unnecessary codes, press the audio button, you will see something like this:
KeyRelease event, serial 34, synthetic NO, window 0x3800001,
root 0x15d, subw 0x0, time 7145078, (-71,-326), root:(523,0),
state 0x10, keycode 121 (keysym 0x1008ff12, XF86AudioMute), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False
The important part is keycode 121, in my case.
Create the file ~/.xmodmaprc and put in it:
keycode 121 = F24
F24 is an arbitrary code chosen by me, you can use whatever you want but i suggest F+number, greater than 12.
Now install xbindkeysrc, you can find it at slackbuilds.org, compile and install.
xbindkeys --defaults > /home/simplex/.xbindkeysrc
to create the default configuration.
Add the part for audio mute/unmute at the bottom:
"amixer -c 0 sset Speaker,0 toggle"
m:0x10 + c:121
Mod2 + F24
Replace the 121 and F24 with your codes, the part in “” is the command that you want to run when the button is pressed, in this case the mute/unmute of our notebook speakers.
Next time, the volume bar!