My ex called me while traveling, putting another author on the line. They'd been talking, she mentioned me and showed her one of my books and one thing led to another. But she told me of her current project. Seems she's both an author and a musician, and she's writing a new score for each chapter of the book she's currently writing. She hadn't investigated how she's going to accomplish it, though.
I told her, the last I'd checked, that the only way to do that is through Apple with their iBooks Author software, which allows you to create multi-media books containing sound, music and video. Otherwise, she could simply publish via the 'normal' channels and simply include an active link at the top of each chapter to access the music (whether for free for pay).
However, I told her it has been a LONG time since I last checked the state of the art. Has anyone heard anything more recently, aside from audio books, which allows music to play in the background, but she'd also need to read her book, and most audio books sell for significantly less than either print or ebooks.