Book excerpt: Vowel harmony is a well known phonological phenomenon found in a large number of languages spoken mainly in Eurasia and the African continent. In simple terms, vowel harmony is a law which governs the co-occurrence of vowels within a span of utterance, nearly always the word. The contributions of this volume focus on various (not always uncontroversial) aspects of vowel harmony that include typological investigations, phonetic/acoustic experimental studies, descriptions of individual systems, genetic and historical ramifications, and implications for a variety of theoretical models. This volume will prove to be a useful guide to the multifaceted issues posed by an often discussed and quite significant phonological process. This volume will stimulate further discussion and better understanding of the issues raised by the intricate process called vowel harmony.