The method we use on our program to speech synthesis do not allow us to add more languages, it depends on the OS and the browser support.
The guide below shows how to download more TTS voices on Windows 10:
https://support.microsoft.com/en-us/help...tts-voices
The guide below shows how to download more TTS voices on Windows 10:
https://support.microsoft.com/en-us/help...tts-voices