The format of the greeting file is called AMR (Adaptive Multi-Rate.) It is a special compression format for speech, so the resulting quality is only fair.
Nah, let's face it: the quality is lousy!
There is a swiss-army-knife OpenSource tool called ffmpeg that can produce .amr files among many other things. FFmpeg is a trademark of Fabrice Bellard.
It is distributed under the GNU General Public License. Copyright © 2000-2006 Fabrice Bellard et al. See ffmpeg.org.
FFmpeg is also used by an application called ffmpegX that wraps a GUI around it and many other useful tools - we'll grab it from there.
Click here to download ffmpegX to your desktop - if this doesn't work, then you need to do it manually.
After the download, click the button below to tell iFuntastic the location of the application or disk image (if necessary.)
iFuntastic will use ffmpeg to convert your greeting to the AMR format.
There is no need to install or run ffmpegX, but if you do, then please register with its author. See ffmpegX.com.