Hello Ico!
why not go for praat? Praat offers many voices related functions. You can
use the easy, funny bits, like changing speaker/gender or I believe trace
different melodies, if there are any to find. You could I think move the
formant filters. A very interesting tool to work with voices. It has a GUI,
but you can also use a simple script language, if you want to do something
clever, based on algorythms. The results are very living, very close to a real
voice, if you want them that way. I liked it, because it didn't sound so
obviously synthesized.
Hope that helps.
Kindest regards
Julien
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