1. A method for use with a speech-enabled application, the method comprising: receiving, from the speech-enabled application, input comprising a plurality of text strings; identifying a first portion of a first text string of the plurality of text strings as differing from a corresponding first portion of a second text string of the plurality of text strings, and a second portion of the first text string as not differing from a corresponding second portion of the second text string; assigning contrastive stress to the identified first portion of the first text string, but not to the identified second portion of the first text string; generating, using at least one computer system, speech synthesis output to render the plurality of text strings as speech having the assigned contrastive stress; and providing the speech synthesis output for the speech-enabled application.