What is story tone? By tone I mean the writer’s imprint of a moral, ethical, and aesthetic attitude on the narrative.
In a nutshell, it is the writer’s choice of the genre of the story, and his work within it, that determines the tale’s tone, and not its plot, theme or setting.
If this were not the case a similar setting in a musical, say, The Rocky Horror Picture Show, and the classical horror, Frankenstein’s Monster, would produce a similar tone in both cases—not one of levity in the former and one of dread in the latter.
“Story tone can be satirical, comic, serious, or tragic. It is strongly influenced by genre. It does not shift the story’s theme and plot on its own.”
Theme
Does tone help to determine the theme of a story? The short answer is no. If we take theme to be the (moral) lesson delivered at the end of the story as a result of the final conflict between the protagonist and antagonist, then it is clear that a musical or a comedy can produce as serious a theme as drama or tragedy. In this sense, theme tends to be a universal and moral element, floating above the specifics of genre.
Plot
What about plot? Here again, tonal elements are shaped not by plot, but by genre: The events at Frankenstein’s castle, for example, may receive a traditional horror treatment, or may be rendered comedic or satirical, as in a musical, giving rise to a different emotional experience. Again, it is genre, not plot, that creates the tonality of the story.
Summary
Although story tone is deeply rooted in the genre of the tale, it is influenced by the writer’s moral, ethical, and aesthetic attitude towards the story and the method of telling it.