Well, I think, I certainly used backward music in Sea of Monsters. I can't remember in the Sea of Time. I would tend to do that all the time, you know? I tended to do all sorts of weird things. Just to get effects. ↗
The truth is everybody does it from time to time. People dial telephone numbers and they get a wrong number only to find that they've read the last two digits backwards. Everybody does it, but dyslexics have this tendency to a higher degree. ↗
When the time comes for your brain to process the information, the second word comes up faster than the first one. So when it's in your head, all of a sudden, it comes out backwards and you think of the word backwards. ↗