Many thanks again! It took some digging this morning on my own to find the directory that you so graciously posted--somehow I knew the answer would be waiting for me when I logged back in! As a side note, it would be great if we could have a central listing of where everything is stored in the directory structure for each device/application in linuxmce. This is often half the battle in trying to get things to work.
My big question still remains how Linuxmce is creating the new announcement as you add users. It seems like it is re-recording the files in that directory as it needs them and then doing a text to speech of the users names in the order they are registered with phone extensions. Anyone that could shed light on how this happens would be a true guru of Linuxmce in my eyes. Lacking that....
If you want to modify your intro on asterisk here is what I have found:
1) As pointed out above, all the voice-menu files are saved as gsm files and located in the directory /var/lib/asterisk/sounds/pluto. Asterisk seems to default to that directory so I didn't have any luck getting any of the files in /var/lib/asterisk/sounds to play with default conf script (listed below in 2). So, if you want to add your own voice menu you should probably consider putting it in there.
2) The file you need in order to tell asterisk where to locate the new voice menu is /etc/asterisk/extensions_pluto_dial.conf and the context is [voice-menu-pluto-custom]. The fourth line down in that context tells asterisk to play the voice menu file: exten => s,4,Background(pluto/pluto-default-voicemenu) and this is the one that has all the users names and #'s included. On my system, it is not really of great audio quality and sounds very computer-speech generated--which is a bit confusing to first-time callers because it is difficult to understand.
3) The other files in the directory which seem to be used to make this file are of quite good quality. If for example, you swap out the line above with the following examples you will get the messages listed:
"Thank you for calling":
exten => s,4,Background(pluto/pluto-default-voicemenu1)
"To call everbody in the house dial 0":
exten => s,4,Background(pluto/pluto-default-voicemenu2)
"If you know the extension, Dial it now":
exten => s,4,Background(pluto/pluto-default-voicemenu3)
"To leave a message press the # sign":
exten => s,4,Background(pluto/pluto-default-voicemenu4)
4) So, if you didn't care about listing the extensions of the users in your home, you could conceivably take these 4 files, join them together, and rename the new file something like /pluto/mashup-intro and use that as the voice intro once you replace the line listed above with your file name. I guess you might also consider just adding them one by one as arguments in the Background command: exten => s,4,Background(pluto/pluto-default-voicemenu1,pluto/pluto-default-voicemenu2, etc.) but I haven't tried that and don't know how that would affect the timing.
5. Alternatively, you could make your own recording based on the extension prompts already listed in the default "pluto/pluto-default-voicemenu" with a recording program that generates gsm or wav files and place it in the directory.
Any other suggestions greatly appreciated.