1. A method for selectively synthesizing speech based on a text string, comprising: at a device having one or more processors and memory: generating the text string from metadata associated with a media asset; parsing the text string and identifying one or more portions of the text string each providing information of a respective attribute associated with or identifying the media asset; substituting at least a first portion of the text string that provides respective information of a first attribute of the media asset with text providing respective information of a second attribute of the media asset different from the first attribute of the media asset, where the first attribute of the media asset and the second attribute of the media asset have been selected according to a genre-dependent rule and a respective genre associated with the media asset; and synthesizing speech for provision with the media asset based on the text string after the substitution.