Kibre examines the phenomenon of initial consonant mutation in Welsh in light of recent advances in several areas of linguistics. He argues that mutations should be considered part of the phonological representations of morphemes. Several sets of mixed mutation types, which seem to call for context-sensitivity in morphemes' mutation characteristics, are accounted for within the framework of Lexical Phonology, particularly through appeal to the Elsewhere Condition. Several 'structural' mutations are accounted for in terms of mutation-triggering but segmentally empty particles. Although rule-based approaches are argued to provide a superior account than can be formulated under a purely constraint-based model, Kibre outlines a mixed model incorporating rules into an Optimality Framework which offers advantages over traditional generative approaches.