Very interesting Sinsy. I tried to play a bit with it and the quality is very high.

Unfortunately when I tried to make it singing very low notes (in english) the result is not good at all.

The reason why I'm interested in low notes is that I would like to create a solfege midi bank for this project

https://github.com/wcgbg/solfege-samples

If you check it, you will see there is already one synthetic voice bank that's done with Alter/Ego. I would like to add synthetic voices. Do you know any other software (free sw) that I could use? Ahem.... I see you're developing one (I read your blog). What about your software?
And do you have any idea how I can improve the quality of very low singing with Sinsy?

Thanks a lot David.
Gianmaria, Geneva