Well, Big Mick, that's a very well-considered statement, and I agree with almost everything you said, especially about Ruby. She was necessary to the story and quite persuasive. I don't think "over the top," because I've known people like that, and suspect there were a lot more of them in the old backwoods.
Only, I'm not sure what you mean about the "role" music had in the book. All I recall about music in the book was that Ada's old man, an old reprobate, suddenly and inexplicably reformed himself by discovering he was a musical genius and became a fine fellow. I've never seen that happen in life. That seemed to me a pretty artificial plot device, but I forgave the author. The film has a couple of scenes with brilliant fiddle playing. It seems to me that gave justice to the musical aspect of the book.