Listen to this [URL="http://www.npr.org/templates/story/story.php?storyId=7489316"]NPR [/URL]radio show to find out how it is done and hear samples. [URL="http://palimpsest.stanford.edu/byform/mailing-lists/arsclist/2005/07/msg00156.html"]Here[/URL]'s some newsgroup-type discussion of it.