Music Theory operates with a host of technical terms for concepts that appear straightforward but that conceal layers of complexity. This collection uncovers some of the richness and intricacy of these terms. Using a range of methods, from philosophical and historical contextualizations to cognitive and systematic approaches, and across a range of repertories, these essays aim to convey a fuller understanding of the terms music theorists employ every day in teaching and research. In so doing, the collection provides a panoramic view of the contemporary music-theoretical landscape, offering new perspectives on established concepts, seeking to expanding their purview to new repertories, and adding new concepts to the theorist’s toolkit. Taken as a whole, the concepts collected in this volume spotlight some of the guiding questions of music theory as it is currently practiced in the English-speaking world; they seek to broaden its foundational conversations to underline the ways in which music theory itself is evolving.