14. The text-to-speech method of claim 13 , further comprising creating a plurality of pitch-modified speech data sets by applying pitch modification to one of the stored speech data sets, and wherein the storing information regarding mappings step stores mapping information in which the depths of objects are mapped to the pitch-modified speech data sets in a one-to-one manner.
13. The text-to-speech method of claim 11 , further comprising storing a plurality of speech data sets and information regarding mappings between depths of objects and the speech data sets.