How is it achieved? Through relays and stuff like that?
You could use a 3PDT plus millenium bypass for the LED.........it's one input and two outputs right?
Well, one input, one send, one return, one out - all stereo.
That's a lot of required switching then. Use relais or CMOS switches I guess.
If the inputs and returns are buffered perhaps you do not need true-bypass switching.
Have a look at the Tine God's 'Wicked Switches', you would need a couple of 4016/4066.