Miglio argues that to assess the relative markedness of a segment, frequency of occurrence in vowel inventories is insufficient when considered on its own. In its analysis of the Great Vowel Shift, this book elaborates a more useful model of a unitary change even in a surface-oriented theory such as optimality theory, with the help of local conjunction. Miglio extends the device of local conjunction to model opaque relations, and calls for reranking and lexicon optimization as the means to capture change within optimality theory.

This book investigates various phenomena affecting both stressed and unstressed vowels in Romance languages. Viola Miglio traces vowel changes within this language family, such as those that occured during the Great Vowel Shift. Using examples from Catalan, Mantuan and Portuguese, this book analyzes vowel reduction, including 'neutralization', which involves a change of vowel quality in stressless syllables that favours vowel qualities that are maximally distinguishable from one another. This analysis provides classifications of vowel reduction phenomena through the interaction of markedness constraints, markedness co-occurance constraints, and faithfulness and positional faithfulness constraints.