Radial Mix Blender, boxed.
"Designed to work with guitar, bass and keyboards, the Mix-Blender sums together two instrument inputs, with individual level controls to balance their relative levels. This allows you to combine two pickups on an acoustic guitar, two effects pedals, or two different instruments on stage so each can be played through the same amp. This combined signal can then be routed to your effects pedals, with a footswitch to activate them in an instant. The effects loop of the Mix-Blender features a unique wet/dry Blend control, which lets you retain the original sound of the instrument and add in as much of the pedals as you like, for effects ranging from subtle to extreme."