9. A speech synthesis system for producing synthesized speech from input text and from input message designators, the system comprising: first and second large speech segment databases referencing speech segments and accessed by segment designators, each speech segment designator being associated with a sequence of one or more speech segments; a segmental transcription database referencing segmental transcriptions associated with sequences of one or more segment designators of the first large speech segment database and accessed by message designators, each message designator being associated with a fixed message; a text message database referencing text messages that correspond to orthographic representations of the segmental transcriptions referenced by the segmental transcription database; a first speech segment selector for selecting a sequence of speech segments referenced by the first large speech segment database and representative of a sequence of segment designators corresponding to a segmental transcription generated responsive to a message designator input; a text analyzer for converting an input text into a representative sequence of symbolic segment identifiers; a second speech segment selector for selecting, based at least in part on prosodic and acoustic features, a sequence of speech segments from the second large speech segment database and representative of a sequence of symbolic identifiers generated responsive to a text input; a message decoder for activating i. the first speech segment selector if a text input corresponds to a text message referenced by the text message database, or ii. the second speech segment selector if a text input does not correspond to a message from the text message database; and a speech segment concatenator in communication with the first and second large speech segment databases for concatenating the sequence of speech segments designated by a segmental transcription from the segmental transcription database to produce a speech signal output.
9. A speech synthesis system for producing synthesized speech from input text and from input message designators, the system comprising: first and second large speech segment databases referencing speech segments and accessed by segment designators, each speech segment designator being associated with a sequence of one or more speech segments; a segmental transcription database referencing segmental transcriptions associated with sequences of one or more segment designators of the first large speech segment database and accessed by message designators, each message designator being associated with a fixed message; a text message database referencing text messages that correspond to orthographic representations of the segmental transcriptions referenced by the segmental transcription database; a first speech segment selector for selecting a sequence of speech segments referenced by the first large speech segment database and representative of a sequence of segment designators corresponding to a segmental transcription generated responsive to a message designator input; a text analyzer for converting an input text into a representative sequence of symbolic segment identifiers; a second speech segment selector for selecting, based at least in part on prosodic and acoustic features, a sequence of speech segments from the second large speech segment database and representative of a sequence of symbolic identifiers generated responsive to a text input; a message decoder for activating i. the first speech segment selector if a text input corresponds to a text message referenced by the text message database, or ii. the second speech segment selector if a text input does not correspond to a message from the text message database; and a speech segment concatenator in communication with the first and second large speech segment databases for concatenating the sequence of speech segments designated by a segmental transcription from the segmental transcription database to produce a speech signal output. 10. A speech synthesis system according to claim 9 , in which the first and second large speech segment databases are the same.