oh, man, if he already has a mixer and a looper (or several) I'd think about having all his instruments running straight into the mixer's input channels, then having the mixer's Aux Send(s) feeding the input to the looper(s) ...and then bringing the looper output(s) back into the mixer via more regular input channel. That way any source can go to any looper -- individually or in combinations -- and any looper can go into any other looper. Or into itself.
I've been doing this exact thing and have been getting a little bit of phasing oddness of having my signal coming through 2 channels after one passes through the looper via aux send and is then the input on another channel. If I play with the mix I can get it to work out, but the settings are weird to me. I'm using an old digi002 board in standalone mode.
