Muting audio

[pinnerite]

I have a remote frontend, receiving its signal from the backend via wifi.

My Linux Mint system has two screens.
I work on right hand one and watch/listen to recordings or live TV on the other.

When the 'phone rings, I would like to be able to mute the sound.
The F9, F10.F11 keys do not do what the listings indicate.

Is there anything i can do to improve matters?

[wesnewell]

Generally, the keyboard only works on the active app running, so switch the active app to the mythtv screen and try it there.