1. A method for producing altered audio output signals, comprising: receiving a selection by a user of an audio data file; loading a text representation of the selected audio data file; providing a first voice signature and a second voice signature; identifying a first speech unit in the text representation, wherein the first speech unit is less than the entire text representation and is associated with dialogue of a first character in the text representation; receiving instructions to apply the first voice signature to the first speech unit; identifying a second speech unit in the text representation associated with dialogue of a second character in the text representation, wherein the audio data file comprises one or more tags that define start and end times of dialogue segments associated with respective characters in the audio data file; and applying the first and second voice signatures to the first and second speech units, respectively, to produce audio for playback.