Thank you so much for this, @RexBeckett !! It works like a charm. Would you mind telling which libraries for Arduino you used? I guess it's too much asked for your code (even though I'm using it for non-profit), but knowing which libraries would help greatly in getting started to make something myself. Anyhow, you've been an amazing help already, thanks again :) Btw, I'm controlling my X18 through USB MIDI, with the X-Touch mini connected to my Windows notebook, running a free software called "Pocket MIDI" which can be downloaded through the Windows App store (or whatever it's called). There, with Ctrl-M one gets the Midi Settings window, where one can map two "Thru" paths, one would be from X18 (listed as "2- X18/XR18 MIDI IN" on my pc) to "X-TOUCH-MINI", the second one would be the other way around, "X-TOUCH-MINI" to "2- X18/XR18 MIDI OUT". So for each, the "Thru" checkbox must be checked. One can minimize this window, it simply pumps the MIDI messages back and forth. One can view them with CTRL-I (Input monitor) and CTRL-U (Output Monitor), best is to also enable "Detail" and "Parser" in File > Preferences.