From the Neapolitan conservatories to Mozart’s Vienna, eighteenth-century musicians commenced the study of harmony by learning a rule of thumb for the harmonization of scalar basses known as the Rule of the Octave. This article presents a series of strategies to incorporate the Rule into the core music theory curriculum, including activities for analysis, keyboard skills, and singing improvisations. I suggest a parallelism between the Rule of the Octave and linguistic collocations (groups of words that typically go together), and turn to recent research on second-language acquisition to defend the importance of memorizing the Rule of the Octave. This initial, apparently rudimentary step conduces to significant learning of tonal harmony. Sharing my personal experiences with the Rule of the Octave in the classroom, I illustrate the potential pedagogical benefits of recovering and updating a teaching resource crucial in the history of Western music.