I look after the sound in my church. At some particular times in the service, the keyboard player wants to cut his line to the mixer and rehearse a bit through headphones.(he is hidden/ not on center stage). What he does is to signal to the guys at the mixing deck and then we cut his line.
I've seen a device on music videos. It is like a foot switch. After a guitarist finishes his song, he switches off his guitar line using that switch, removes his output pin and walks away.
I've tried to search for such a device on the internet but with no success. Any body has any idea about this ?