update needed on software synthesizers for linux

[krishnakant Mane]

so the bottom line is festival is the best option around as open source.
Please tell me out of experience and general feedback, which voices
should I download along with festival and from where I can get these
voices.
I will like to have English UK and US.
further more I want to develop voices for Indian languages like Hindi,
 is it possible.
thanks,
Krishnakant.