I've already mentioned here on the blog a few voice synthesizer software, like Espeak (which provides a voice to my screen reader program), the Japanese voice synthesizer Open JTalk (which the Windows screen reader NVDA uses to read Japanese text), and the singing synthesis software VOCALOID, which I've been using for a while. There's another Japanese voice synthesiser program (both for speech and for singing) called CeVIO. Today I stumbled on this video about Japanese speech synthesizers, and I thought it's very interesting. It begins introducing a few software that came first (MMDAgent and Open JTalk), then goes on to talk about the main topic, CeVIO. It demonstrates various voice samples (both for speech and for singing), and examples of how to edit the voices' parameters to read Japanese text. (it even has tips for those wanting to buy the software :D )

https://www.youtube.com/watch?v=k6c4p8Pjdf8