slackbuilds/accessibility/speech-dispatcher

Speech Dispatcher is a device independent layer for speech synthesis
that provides a common easy to use interface for both client
applications (programs that want to speak) and for software
synthesizers (programs actually able to convert text to speech). To
use Speech Dispatcher, you will also need a Software synthesizer, such
as espeak, flite (available on Slackbuilds.org), or festival (not
available on Slackbuilds.org).

festival-freebsoft-utils is an optional dependency.