There's a book review in our paper today (ew, and it also says, "He pours over several shelves of books...") in which one sentence reads, "By this point there can be little doubt that we are involved in a modern melodrama, but not the kind with organ stings and blatant overacting."
Can anyone tell me what is meant by 'organ stings'?
The review is for The Prisoner of Heaven , the third in what is to become a tetralogy about "The Cemetery of Forgotten Books" by Carlos Luis Zafon. Anybody know this work?

Maybeso, Jackie.
Reading the context of his use of the term a "organ sting" might be the sudden introduction of organ music to highlight the intended drama of a play or a movie.

Did you cringe when you first heard Bach's Toccata and Fugue in the 1931 film "Dracula"?
Yeah, me too.

I've not heard the term 'organ sting' but I like your theory jenny jenny

While I was never scared of Dracula I do think about sharks when swimming in the ocean.
The main "shark" theme, to JAWS, played on a tuba, uses just two notes and has become synonymous with approaching danger.

A quick googling shows the phrase being used in many contexts in a way that supports jennyjenny's conjecture.

https://duckduckgo.com/?q=%22organ+stings%22