GiellaLT provides an infrastructure for rule-based language technology aimed at minority and indigenous languages, and streamlines building anything from keyboards to speech technology. Read more about Why. See also How to get started and our Privacy document.
eSpeak NG Text-to-Speech is a formant-synthesis text-to-speech engine. It does give a robotic voice, but is relatively fast and simple to get going. It may thus be an interesting alternative, at least in initial trials.
https://github.com/espeak-ng/espeak-ng
When building espeak-ng using macports libs, configure as follows:
./configure LDFLAGS=" -L/opt/local/lib"
The rest as documented.
I have not yet tested make install, which may require additional
adjustments.