Good blog post and audio samples notwithstanding, annoying that they don't put the paper on Arxiv. As they themselves point to in the blog post, the learning architecture was introduced in 2014's "Deep mixture density networks for acoustic modeling in statistical parametric speech synthesis" so it's not clear how much of this is just good engineering vs novel research.
The paper was more than likely embargoed until the talk they gave about it was over. They're introducing some new things that they probably didn't want to release details on before they publicly made a statement.
