This circuit works with a normally closed switch. Used a 2Mohm resistor and 2 10M max ohm LDR resistor as a shunt that kills the click sound. The audio does not get cut off. When the Normally closed button the audio goes through the 2M ohm resistor. The volume is dropped and toggle between the two. Sort of like how Tom Morello mutes one pickup and toggles between the two. The 2M resistor can be tweaked lower, some sound leaks . It sound great on clean guitar but may need to be tweaked a bit to make the volume a little lower. Through hi gain amp, it sounds a bit muddy.