1. A computer-implemented method of performing text-to-speech (TTS) processing, the method comprising: receiving text including a first text portion and a second text portion; performing unit selection on the first text portion to determine a first set of speech units representative of the first text portion; performing unit selection on the second text portion to determine a second set of speech units representative of the second text portion; providing preliminary TTS results to a user, the preliminary TTS results based at least in part on the first set of speech units and the second set of speech units; receiving input data corresponding to a correction to a portion of the preliminary TTS results, the portion of the preliminary TTS results corresponding to the first text portion; processing the input data to determine an audio characteristic corresponding to the correction; determining a modified first set of speech units that correspond to the first text portion, wherein the modified first set of speech units corresponds to the audio characteristic and comprises a joining speech unit selected based at least in part on the second set of speech units; determining output data using the modified first set of speech units and the second set of speech units; and causing audio corresponding to the output data to be output.