That AUX in is a lifesaver, and why I bought the Digitech a few years ago. To add the harmonizer to my rack, I had to loose a space that used to house an effects unit. Now, other mics or instruments can share the same great effects that MY voice has on it !
I have it in a three space rackbag with a TOA single space stereo mixer. Smallest, hippest PA bag in town !