The history of music theory, as it has usually been taught in the United States, has focused on a small canon of texts written mostly in Latin, Italian, French, and German. This article advocates a more expansive view of the subdiscipline's remit by way of three case studies. The first considers the distinction that Abū Nasr Muhammad ibn al-Farakh al-Fārābī draws between the speculative and active parts of music theory and its influence on the formation of the discipline in the Latin-speaking world. The second considers entanglement between French and Chinese music theorizing in the later eighteenth century. The third treats the international contexts of Hugo Riemann's thought. I present these three case studies, together with more general reflections on the possible scope of research on historical music theory, with the aim of inviting reflection on the subdiscipline's past, present, and future.