1. A method comprising: receiving text data; determining text segments of the text data, the text segments including a first text segment and a second text segment; determining a first number of different phonetic units of the first text segment; determining a second number of different phonetic units of the second text segment; determining the first number is greater than the second number; sending, through a web-based interface based on the first number being greater than the second number, the first text segment to a first proofreader; receiving, through the web-based interface, an indication of approval of the first text segment from the first proofreader; adding the first text segment to a text-to-speech (TTS) corpus, the TTS corpus comprising approved text segments; determining a third number of different phonetic units of the TTS corpus comprising the first text segment; determining the third number is less than a desired number of different phonetic units of the TTS corpus; and sending, through the web-based interface based on the third number being less than the desired number, the second text segment to a second proofreader.