15. A computer-readable storage device having instructions stored which, when executed by a computing device, cause the computing device to perform operations comprising: receiving text as part of a text-to-speech process; selecting a speech segment associated with the text, wherein the speech segment is selected from a primary speech database which has been modified by: identifying primary speech segments in the primary speech database which do not meet a need of the text-to-speech process, wherein the primary speech segments comprise one of half-phones, half-phonemes, demi-syllables, and polyphones; identifying replacement speech segments which satisfy the need in a secondary speech database; and enhancing the primary speech database by substituting, in the primary database, the primary speech segments with the replacement speech segments; and generating speech corresponding to the text using the speech segment.
15. A computer-readable storage device having instructions stored which, when executed by a computing device, cause the computing device to perform operations comprising: receiving text as part of a text-to-speech process; selecting a speech segment associated with the text, wherein the speech segment is selected from a primary speech database which has been modified by: identifying primary speech segments in the primary speech database which do not meet a need of the text-to-speech process, wherein the primary speech segments comprise one of half-phones, half-phonemes, demi-syllables, and polyphones; identifying replacement speech segments which satisfy the need in a secondary speech database; and enhancing the primary speech database by substituting, in the primary database, the primary speech segments with the replacement speech segments; and generating speech corresponding to the text using the speech segment. 19. The computer-readable storage device of claim 15 , wherein the primary speech database comprises first voice recordings in a first dialect, and the secondary speech database comprises second voice recordings in a second dialect, wherein the first dialect and the second dialect differ by one of dialect differences, geographic language differences, regional language differences, accent differences, national language differences, idiosyncratic speech differences, and database coverage differences.