1. A method for creating an audio index representation of an audio file from text input in a form of a text string and producing the audio file from the audio index representation, the method comprising: receiving the text string; converting the text string to an audio index representation of an audio file associated with the text string at a text-to-speech synthesizer, the converting including selecting at least one audio unit from a first audio unit synthesis inventory having a plurality of audio units, the selected at least one audio unit forming the audio file; representing the selected at least one audio unit with the audio index representation; and reproducing the audio file by concatenating the audio units identified in the audio index representation from the first audio unit inventory or a second audio unit synthesis inventory having the audio units identified in the audio index representation.