eSpeak is a compact open source software speech synthesizer for English
and other languages.

eSpeak produces good quality English speech. It uses a different synthesis
method from other open source text to speech (TTS) engines, and sounds
quite different. It's perhaps not as natural or "smooth", but some find
the articulation clearer and easier to listen to for long periods. It
can run as a command line program to speak text from a file or from stdin.

portaudio is optional but highly recommended: To actually produce audio 
output, this package requires portaudio.  Without it, espeak will only be 
able to render speech to a wav file (which may still be useful to you).

To build without portaudio support, set WAVONLY=yes in the script's
environment.