A system and method for adding audio indicators, such as an audio tone, to audio data corresponding to text. The audio indicator corresponds to secondary content in text, such as a footnote. The system will insert and/or modify a textual indicator at a location in the text corresponding to the secondary content. The system will then process the textual indicator during text-to-speech processing of the text so that an audio tone is output at a moment in speech data corresponding to the location of the secondary content in the text. A speech synthesis markup language may be used to create and/or modify the textual indicator.