How do I add more voices in speech synthesis?

Hi everyone

I am making a project which uses text to speech synthesis. It is awesome. But there is a small issue

I want to add more voices (I know that it will require tweaking with chrome). Can someone help me out how to do it?

I do not have to worry about user-side as the program is only meant to run on my pc ( actually I am making it for a blind people charity )