festival.el provides a simple interface into the festival speech
synthesis program from
Emacs Lisp.
BTW, it was only once I'd more or less finished writing the first version
of this that I noticed that a festival.el comes with festival itself
(yeah, I know, I should spend more time examining the contents of
software packages). As it is, I decided to press on with this anyway
because I'd done a couple of different things and, more importantly, I
was having far too much fun.