You hit on it in your reply. And I do not say this lightly.... I despise this about myself -
I do not remember novels the way most people do. I remember the emotions they brought out in me. I remember the physical act of reading them... often WHERE I read them. But the plots? Only rarely. Quotes? Almost never. When a book is brought up on this board, or in conversation, that I have read I nearly always need to have the person give me a synopsis, and usually more than a brief one, before it begins to 'come back'.
You ask if the "reel to reel played backwards" scene is in the novel. I don't know. I can't remember. And even though it's true that I read the novel only once and that back in the 70's... that's no excuse. Most people, and I say that literally, remember entire novels no matter how much time has passed by.
And we're talking "The Exorcist" here, a novel I loved. Bought it late one afternoon and finished right about dawn of the next day. True that I remember it somewhat well... compared to most books I've read... but it's the 'experience' of reading it that I recall well... particulars I remember very poorly.
With a few novels, books, I have remembered... remembered in the way most people remember books they've read that is... but the ratio of those I remember well to the number I have read is just sickeningly low.
Another good point you make... King, as I mentioned, has been brilliant. Granted. But some, most for me, are just terrible. I can't understand or rationalize that spread.... thus... gotta be me just 'missing it'.