KMouth itself does not contain a speech synthesizer. Instead it assumes that a speech synthesizer is available in the system. Currently it either uses any shell command specified by the user or the the text-to-speech interface of KTTSD. (KTTSD, the KDE Text-To-Speech Daemon, a plug-in based KDE project that wants to provide both a standard text-to-speech interface for KDE applications and a simple-to-use configuration dialog for the user.)