This is not really an NVDA question - it's more of a synthesiser question, so
please tell us which synth you use (and perhaps which other synths you feel
happy with) so people might be able to advise how to do what you want.

It might also be helpful to mention which non-English language/s you wish to
adjust the pronunciation of.

Antony.

--
Please apologise my errors, since I have a very small device.

Please reply to the list;
please *don't* CC me.