This article follows a change in pronunciation of word-medial intervocalic /t/ in New Zealand English, as it unfolds over 120 years. Data are analyzed in the context of questions about the role of experience-based lexical representations and their potential impact on the time course of sound change in progress. Three major results are reported. First, frequent words lead the change. Second, the distributions of individual words affect their participation in the change: words favored by younger speakers are produced with newer variants. Finally, the topic of conversation affects which variant is favored: older topics elicit older variants. Together, these findings provide evidence that phonetic distributions of word-level representations are implicated in the course of sound change.