Thanks for these great ideas. After many experiments @joecozzi got me closest to a solution with that little dip switch on the bottom. I’m still working just with the synth pedal and have not yet reintegrated the way. A couple of issues remain. Probably the first and for sure the second have more to do with the accordion and the synth pedal than with any Mixinglink setup. First, on 90 percent of the synth sounds I get all these sound artifacts playing through the system even when I’m not playing the accordion. It’s almost like the synth is broadcasting a radio signal of a given effect to the phones/monitor/amp, even after I’ve carefully adjusted the gain. Or perhaps the pedal is picking up and digitizing any random exterior sound that enters the accordion chamber. If anyone has any suggestions about this problem, I’m all ears, but again I recognize it’s probably not a Mixinglink issue. Second, as would be expected, most of the synth effects are very guitar-focused and 80s-like. I’ll have to decide whether the few that really fit the accordion and the jazz/blues/world orientation of my band make it the right pedal. I’m going to try a couple of other pedal options. The good news is that I now know how to use the Mixinglink to its best advantage. Thanks again!

A couple of other things:

For @joecozzi: your solution worked well even when mixing the dry and wet sound.

For @PRSGUY513: yes, I’ve been using the wah successfully for years now. At first it was a challenge to make it work without terrible feedback. The mixer proved to be the solution to that problem.