The eSpeak NG is a compact open source software text-to-speech
synthesizer for Linux, Windows, Android and other operating
systems. It supports more than 100 languages and accents. It is based
on the eSpeak engine created by Jonathan Duddington.

eSpeak NG uses a "formant synthesis" method. This allows many
languages to be provided in a small size. The speech is clear, and can
be used at high speeds, but is not as natural or smooth as larger
synthesizers which are based on human speech recordings. It also
supports Klatt formant synthesis, and the ability to use MBROLA as
backend speech synthesizer.

Homepage:
https://github.com/espeak-ng/espeak-ng/
