17. A speech synthesis system as set forth in claim 16, wherein said digital speech data stored in said memory means comprises digital speech data representative of sound units; and further including concatenating controller means connected to said memory means and interposed between said memory means and said voice characteristics conversion means for stringing together sequences of digital speech data representative of allophones to define respective series of said digital speech data representative of words for input to said voice characteristics conversion means.
17. A speech synthesis system as set forth in claim 16, wherein said digital speech data stored in said memory means comprises digital speech data representative of sound units; and further including concatenating controller means connected to said memory means and interposed between said memory means and said voice characteristics conversion means for stringing together sequences of digital speech data representative of allophones to define respective series of said digital speech data representative of words for input to said voice characteristics conversion means. 18. A speech synthesis system as set forth in claim 17, wherein said digital speech data representative of sound units stored in said memory means comprises digital speech formants; said speech synthesizer means being a linear predictive coding speech synthesizer; and further including parameter look-up means interposed between said voice characteristics conversion means and said linear predictive coding speech synthesizer for converting the modified digital speech formants output from said voice characteristics conversion means to digital speech data including digital speech parameters representative of reflection coefficients for input to said linear predictive coding speech synthesizer.