In my continuing quest to research research research the topic, I read this but I'm sorry to say that for the mosr part, I found it tiresome and ridiculous. Here is a more eloquent discussion of its virtues than I have the appetite to pen. 

However, I did get one thing from it which was an interesting thought that rather than melodic, harmonious, wondrous, Joan may have found the sudden and unexpected appearances of all of these saints something like terrifying. Something even (heaven forfend, literally) like possession. Which is quite a thought.

So I entreated our Joan to read chapter eight which describes this (and ignore all the awful stuff about skin scarring and anatomically accurate observations about female peculiarities). And this lead her to message me this morning with her thoughts about the voices and how they might make the character feel. So Book of Joan, I thank you. You've added something to proceedings, even if it weren't quite what I'd hoped and expected.