I would be interested in their reaction to two notes being played which are just slightly out of tune. Because it definitely seems like something which can be trained - professional musicians often have a pain-like reaction to it, while your Average Joe just notices that it sounds bad. But at the same time, your Average Joe still notices that it sounds bad, and yeah, just like with dissonances, it's hard to imagine s…
Take a gander at an actual 17th century composer playing with that idea in a most audacious way [0]. The section of the piece I'm referring to begins around 3:26. The idea seems to be, keys that are foreign to the piece should sound dissonant. [0]: https://www.youtube.com/watch?v=BbrrMtWICs4
That is wild. Thanks for sharing.