"You say that, "Anytime one of the switches is closed, the other 2 should open.""
Yeah, I said that but I was wrong. Switches 1 and 3 are closed when switch 2 is closed. Been a long and busy weekend.
"Does he have a couple of [guitar] effects that he wants to engage with foot switches, like hit switch 1 and effect 1 comes out, hit switch 2 and effect 2 comes out and hit switch 3 and both effects (or neither) come through? Inquiring minds want to know!-) "
That's exactly it, but at no time should both effects be working. Switch 3 (switch 2 in the diagram) would simply be a bypass switch for the entire device. Once either effect switch is engaged the bypass switch would open.
I haven't meant to be so vague. You just put it in better words than I did. For that, I thank you.