how to configure f_mixer function in NsCDE?

[sonicfon]

[CyberCois]

TBH I could not figure out how to get f_Mixer to work.
So I put this in my Keybindings.fvwmlocal:

Silent Key XF86AudioLowerVolume A A exec mixer -f /dev/mixer vol.volume=-0.02
Silent Key XF86AudioRaiseVolume A A exec mixer -f /dev/mixer vol.volume=+0.02
Silent Key XF86AudioLowerVolume A C exec mixer -f /dev/mixer vol.volume=-0.02
Silent Key XF86AudioRaiseVolume A C exec mixer -f /dev/mixer vol.volume=+0.02
Silent Key XF86AudioMute A A exec mixer -f /dev/mixer vol.mute=^

The exec part will be different based on what you are using for system audio. I'm using OSS on FreeBSD.
If it still says you need to define f_Mixer for some reason you can just set it up to do nothing in Functions.fvwmlocal