Perfect synthesis for all of the people all of the time

The quality of speech synthesis has drastically improved over the last ten years. Or at least it appears that this is the case. We have moved from diphones to unit selection. However, although we can produce much more natural sounding examples we have also given up an certain amount of control over what can be synthesized. We have reached the stage where playing a few examples to a non-expert can easily convince them that speech synthesis is a solved problem. This paper looks at how we might not only convince some of the people some of the time, but what we must do to produce perfect synthesis for all of the people all of the time.