key "Ctrl+KP_Divide" amixer set Front 5%- # lower sound
key "Ctrl+KP_Multiply" amixer set Front 5%+ # raise volume
key "Ctrl+0" amixer sset Master,0 toggle #mutes sound
IOW, to increase volume press the asterisk on the numerical pad to the right of the kbd.
to decrease sound pree the slash forward.
and to mute, Ctrl + 0 as before.
I configured the sound to my liking with alsamixer:
# alsactl store
PS: the original volume keybinds (ctrl + up/down arrows work fine in JWM)