IntroductionData on phonological developments in Highlands Mixtec dialects 1 indicate that the inclusion of a level of phonological constituency beyond the syllable can greatly simplify the characterization of the key sound changes in these di alects. While higher-level phenomena, most often in the guise of the root, have long been of interest in historical linguistics -cf. especially the Root Structure Constraints of Proto-Indo-European -, such diachronic matters have gener ally not been analyzed within frameworks able to address such high-level is sues elegantly. 2 By developing and applying the notion of the prosodic tem plate explicitly in language change and incorporating it into recent phonological theory, ultimately we can achieve a more coherent and parsimonious under standing of sound change. The goal of this paper is to take a step in that direc tion.While synchronic phonological theory has spent much of the last 15 years or so exploring views of phonology above the segment, i.e., syllable-level and higher-level prosodic matters, historical linguists have overwhelmingly re mained focused on matters below the syllable, and standard handbooks in the field do not yet include explicit discussion of structure above the segment. * We are grateful to the following people for a broad variety of comments, suggestions discussions and other help on this topic and this paper: