Thank you for the explanations - now I just need to think them through.
PS - I've just got an Akai MIDImix
and am very grateful for your MIDImix oscii-bot script. When I'm brave / knowledgeable enough I'll have a look at some ideas I have for that script too.
Meanwhile, I'm working on this at the moment:
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https://i.imgur.com/lrzDUHo.png