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. 18. The computer-readable storage device of claim 15 , wherein the primary speech database has been further modified by identifying boundaries of the primary speech segments.