How to kill an hour on a Mac on a rainy afternoon?
- open Terminal.app
say -v ?(to list all the voices installed) or
say -v ? | grep en_(for English-only)
say -v Fred Fitter. Happier. More productive.
And if you want more voices, or better ones (some do have an upgrade) find the Speech section of the Accessibility panel of the System Preferences.
Expand the System Voice drop down and marvel at the Customize... option.