1. A method for speech synthesis in an electronic speech synthesis system, the speech synthesis method comprising: a) storing in a memory of the electronic speech synthesis system a voice table comprised of a set of phonetic waveforms, each phonetic waveform of the set of phonetic waveforms corresponding to a demi-diphone of the voice table; b) receiving as an input to the electronic speech synthesis system a phonetic string representative of speech to be synthesized by electronic speech system, the phonetic string comprising diphones, the diphones comprising demi-diphones; c) generating synthetic speech of the phonetic string representative of speech in the electronic speech synthesis system by outputting stored voice table phonetic waveforms by: i) retrieving a stored voice table phonetic waveform corresponding to a demi-diphone of the input phonetic string representative of speech in the case of the demi-diphone of the phonetic string representative of speech having a phonetic waveform in the voice table corresponding to the demi-diphone; ii) retrieving a stored voice table phonetic waveform not corresponding to a demi-diphone of the input phonetic string representative of speech in the case of the demi-diphone of the phonetic string representative of speech not having a phonetic waveform in the voice table corresponding to the demi-diphone by locating a substitute demi-diphone of the voice table having a corresponding stored voice table phonetic waveform which has phonetic features meeting: A) a threshold set of phonetic features of the demi-diphone not having a corresponding stored voice table phonetic waveform, wherein the threshold set describes a minimum set of characteristics that must be share d by: 1) the demi-diphone of the phonetic string representative of speech not having a phonetic waveform in the voice table corresponding to the demi-diphone and, 2) the substitute demi-diphone of the voice table having a corresponding stored voice table phonetic waveform; and, B) the most features in common with the demi-diphone not having a corresponding stored voice table phonetic waveform.