What software did Ebert use? I remember him talking about paying English researchers to synthesize his own voice, but I don't think anything materialized.
http://www.rogerebert.com/rogers-journal/finding-my-own-voic... https://www.cereproc.com/
https://www.youtube.com/watch?v=_0KUw3xr7cA
And it wouldn't be possible for Hawking. Ebert's system was put together using hundreds of hours of recordings from Skiskel & Ebert At the Movies.