[Zikes]

The Japanese language is fairly different from English, so much so that it can be synthesized so well that they have entirely virtual pop music stars.

https://en.wikipedia.org/wiki/Vocaloid#Singer_Library

[daeken]

Vocaloid's English support has gotten absolutely fantastic. If you're curious, here are a couple of my favorites: https://www.youtube.com/watch?v=EMc4kw45e5g https://www.youtube.com/watch?v=XmifuQvFu8M https://www.youtube.com/watch?v=cQKGUgOfD8U

They're not for everyone, and the voices are still mechanical, but I've become a huge fan of English Vocaloid, especially Gumi.