eSpeak

A compact, open-source software speech synthesizer supporting over 100 languages and accents through formant synthesis.

eSpeak delivers high-speed text-to-speech (TTS) functionality across Linux, Windows, and Android. It utilizes a formant synthesis method, allowing the engine to remain tiny (under 2 MB) while providing clear articulation at high words-per-minute rates. The system supports the SAPI5 interface, works as a command-line tool, and acts as the default voice for the NVDA screen reader. Developers leverage its C++ library to integrate multilingual support (including Cantonese, English, and Swahili) into resource-constrained environments.

https://espeak.sourceforge.net/