app_festival is an application that allows one to send text-to-speech commands to a background festival server, and to obtain the resulting waveform which gets sent down to the respective channel. app_festival also employs a waveform cache, so invariant text-to-speech strings ("Please press 1 for instructions") do not need to be dynamically generated all the time. You need : 1) festival, patched to produce 8khz waveforms on output. Patch for Festival 1.4.2 RELEASE are included. The patch adds a new command to festival (asterisk_tts). It is possible to run Festival without patches in the source-code. Just add this to your /etc/festival.scm or /usr/share/festival/festival/scm: (define (tts_textasterisk string mode) "(tts_textasterisk STRING MODE) Apply tts to STRING. This function is specifically designed for use in server mode so a single function call may synthesize the string. This function name may be added to the server safe functions." (let ((wholeutt (utt.synth (eval (list 'Utterance 'Text string))))) (utt.wave.resample wholeutt 8000) (utt.wave.rescale wholeutt 5) (utt.send.wave.client wholeutt))) [See the comment with subject "Using Debian festival >= 1.4.3-15 (no recompiling needed!)" on http://www.voip-info.org/wiki-Asterisk+festival+installation for the original mentioning of it] 2) You may wish to obtain and install the asterisk-perl module by James Golovich , from either CPAN, or his site: http://asterisk.gnuinter.net, as this contains a good example of how variable text can be tts'd via asterisk, namely the examples/tts-*.agi files there. It has been noted that the current expression evaluation capabilities of asterisk are not best suited for the generation and manipulation of text. AGI scripting can be ideal for these sorts of needs. For simpler usage, fixed, pre-recorded messages may be more amenable for your purposes. 3) Before running asterisk, you have to run festival-server with a command like : /usr/local/festival/bin/festival --server > /dev/null 2>&1 &