1. A concatenative speech synthesizer, comprising: a database containing (a) demi-syllable waveform data associated with a plurality of demi-syllables and (b) filter parameter data associated with said plurality of demi-syllables; a unit selection system for extracting selected demi-syllable waveform data and filter parameters from said database that correspond to an input string to be synthesized; a waveform cross fade mechanism for joining pairs of extracted demi-syllable waveform data into syllable waveform signals; a filter parameter cross fade mechanism for defining a set of syllable-level filter data by interpolating said extracted filter parameters; and a filter module receptive of said set of syllable-level filter data and operative to process said syllable waveform signals to generate synthesized speech.