Do you ever think about how Hyde knew the story about Für Elise, but mentioned to Iris that he knows nothing about classical music?
Headcanon that back when he pretended to be a regular hedgehog, Licht would tell him everything about the pieces he was playing, from history over techniques of playing to his personal opinion. Hyde usually wouldn't really listen, but turns out he picked up quite some information without realising.
And one day, months after forming their contract, Hyde overhears Crantz talking about music theory or Licht struggling with a difficult part of a new piece and casually goes "actually this is wrong" or "if you tried ___ it might work better" without looking up from his phone
And Licht and Crantz both pause to stare and him and go "why do you know that??" (because Licht would totally forget that the demon is still the same being as the hedgehog he picked up) and all Hyde can answer is "I?? don't know??"
Meanwhile Guil sips coffee in a corner and says "yeah you've always been like that"