This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book presents a different type of visual evidence, that of sixteenth-century art theory, and demonstrates its relevance to debates among music theorists. It examines a brief melisma from the plainchant Pastor cesus, an antiphon from a late twelfth-century rhymed office for Thomas Becket. The book provides instructions for carrying out ritual or ceremonial events – including music performance – in the form of rubrics. It shows how certain concepts and debates in sixteenth-century art theory are closely echoed in the writings of music theorist Vincenzo Galilei, particularly in his Discorso intorno all’opere di messer Gioseffo Zarlino da Chioggia. The book focuses on dance, an important setting for much secular music-making during the Middle Ages and Renaissance, and one in which visual and aural aspects are closely combined in performance.