Actually, I know exactly what tradition this book is in. It's magical surrealism, a genre that you know best as "that stuff Daniel Pinkwater writes". (Pinkwater is of course an attested Dadaist; there's an essay about this.) Pinkwater's stories concern kids falling into a world of absurdity, which they accept wholeheartedly because childhood is continuously absurd. Well, imagine dire old ladies doing the same thing -- second childishness, equally absurd -- and that's The Hearing Trumpet.
I don't think I'll bother thumbnailing the plot. As I said, it's got reams of everything, and nothing like a structure you'd expect. I suspect half of it is a direct reflection of whatever the author was cranky about that day (Theosophists and patriarchy?) and whatever she had a kink for (nonconforming women). You take a running leap at the rabbit-hole and see what you get.