It hurts me to advocate Windows but using tcom with the free speech engine from Microsoft is almost too easy (yes I know Microsoft and free speech sounds like an oxymorin :)

 package require tcom
 
 set voice [::tcom::ref createobject Sapi.SpVoice]
 
 $voice Speak "Hello World" 1
 
 after 3000
 exit

The speech SDK is available from http://www.microsoft.com/speech/download/sdk51/ (51MB), there is a beta of .Net Speech at http://www.microsoft.com/speech/ (200MB) but I haven't tried that yet. - VPT


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[GPS] [Rsynth] is a nice public domain package that I've used for speech synthesis.  I wrote a say_this.tcl script that built a GUI for tweaking the voice.  I've been thinking about improving Rsynth, because it seems to be at the moment dead.  Another tool that I've heard good things about was Festival[http://www.cstr.ed.ac.uk/projects/festival/].  CMU's Sphinx[http://fife.speech.cs.cmu.edu/sphinx/] is another tool that may be good, but I haven't heard from users of it.

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Tcl'ers may be interested in the [CSLU Toolkit] [http://cslu.cse.ogi.edu/toolkit/] developed at the Oregon Graduate Institute's Center for Spoken Language Understanding.  It includes a [RAD] environment which supports Tcl and provides tools to do [Speech Recognition] as well as speech synthesis. -- [aricb]