Writing Journey: Pronunciation Guides

Up today: Answering a question L. T. Eliot (also known as Lexicon Luvr) posed some time ago:
[Writers creating pronunciation guides for audio recordings:] is a new phenomenon to me, and I've only ever heard it mentioned once. How long has that been going on?
I can't speak for other writers and their experiences with their publishers, of course, so what comes below is based on my experience.
For my first five books, Covenant released an audio version on either cassettes or CDs (in one case...