A. I wish I knew how to express the tonality. (Is “tone” the right word?)
B. Has anyone else noted this?
C. into what file does this kind of development in language go; it is not a neologism, obviously.
As for “seriously?” maybe ‘cadence of inflection’ might be a better choice than simple linear “tonality,” or intonation, though tonality seems to cover it except for what I hear as rising inflection indicating the incredulity and the question. It may be related to the recent habit of using an inflection generally reserved for a question in the middle of a sentence, seemingly to elicit agreement possibly with an eye to emotionally entraining the audience in order to gain easier acceptance. Not that there is anything controversial usually being said. Used mainly by women, I seem to recall in my mind’s ear, and I think, “valley girl” of the 1980’s. Wikipedia suggests “uptalk, upspeak, rising inflection or high rising intonation (HRI)” (see link below) Intonation, but requiring some indication of tone relationship or relative pitch over time. There may indeed be an elegant linguistic notation for something like this. As a layperson I am clueless about this.
B: I have often asked, and have been asked, “Humph. ...(slight pause)… Are you serious?” after a raised eyebrow. I thought it might be interchangeable with “… Seriously?” And I’ve heard it as you describe, “Really? Seriously?” In the US, can’t mail down a time or place but certainly since around the mid 1980’s.
It might be put into the ”High rising terminal” intonation file area if there is such a thing.
I think the spirit of the title of the following book as I read it captures a version of it well:
”Surely You’re Joking, Mr. Feynman!”: Adventures of a Curious Character, 1985 an edited collection of reminiscences by the Nobel Prize-winning physicist Richard Feynman.