Change in physics, mind, space or time.
Obviously, these coexist. With a jump in time, the mind of a character will be unrecognizable. Ed Harris and his younger counterpart in Westworld. This is magnified by have two different actors. Are we not two different people after the passage of time?
When talking about WOZ, I wonder if that tonal shift is reflected in more than just subject material: mundane to fantasy?
I'm reading a book that may become one of my favorites: Three Body Problem by Cixin Liu. In the beginning of this book, a few time shifts really reflect this idea of tonal shift.
Also, there are some significant shifts in space and mind as well. I'm only six or seven chapters in... but I feel it coming.
Without a jarring shift in time, space, physics or mind, it might need or seem to be gradual. Otherwise, it could be interpreted as madness.
The Harry Potter series shifts in tone from movie to movie or book to book.
In terms of mind, I think perspective must create a tonal shift if done correctly? No?
In the Westworld example, time brings about the change in one mind. This covers both. If we are talking about a change of space, two different people, then it wold be just as abrupt.
Well, there's more there I think, but I tend to get confused the more I write.
My recommendation would be the book I mentioned above or any story that shifts dramatically in time, space, mind or physics.