Hello Lowboy, hope all is well and the gigs are plentiful. It sounds like your biggest issue is actually going to be your microphone. I have yet to get decent amplification or should I say “controlled” amplification with a microphone and amplifire. It’s much different with a decent sound system and decent board man. You need to be able to hear your sound from your amplifier to be able to mix yourself into the band overall mix. I jammed a few weeks ago where we had (2) trumpets, sax, electric bass, guitar, keyboard and drums and I was asked to trim down a bit simply because where I was seated I could not hear the overall mix and I was using a small fender Acoustasonic junior, talk about a lack of power. I heard myself but could not hear all the instruments evenly (no engineer) just a Bose system for vocals and the keyboard and horn solos. Monitors help but you still need to be heard. I would go to a pickup since you have sound holes in the back of your melodica. Unlike your piano 36 that the sound comes out of the keyboad much harder to pickup with a microphone. I would invest on the Myers pick up and run it through your rig. It may work for you. I can not say with 100% accuracy since I do not have a piano 26 and cassotto. It does work great with the pro 36. Sorry if I sound like a salesman.