The precise sense of Jean Philippe Rameau’s conception of supposition is among the more vexing questions that his theorizing poses. Supposition has been interpreted, on the one hand, as an account of ninth and eleventh chords and, on the other, as a means of explaining melodic suspensions. Understanding Rameau’s doctrine means, in part, retracing the many refinements, revisions, and reversals that it underwent over the course of its author’s career. This article accordingly reconstructs the development of supposition from the Traité de l’harmonie (1722) to the Code de musique pratique (1760), with particular attention to the extensive discussion of the topic in the “Art de la basse fondamentale” (c. 1737–43). To a considerable degree, Rameau’s conception of supposition was worked out in dialogue with his critics. Retracing that dialogue helps to clarify a number of points: First, Rameau revised his account of supposition continually. Second, the impetus for these revisions was, in many cases, the intervention of a prominent critic. Third, these critics did not, as has been claimed, misunderstand Rameau’s account of supposition; rather, they disputed it (the second musicien) or extended it (Charles-Henri de Blainville and Jean-Jacques Rousseau). Fourth, the eventual form that Rameau’s doctrine took was significantly influenced by these criticisms; indeed, Rameau tended to appropriate those aspects of his interlocutors’ arguments that he ended up finding germane. And fifth, it emerges from this inquiry that supposition is not solely a means of accounting for melodic suspensions; it is also an attempt to explain a number of idiomatic sonorities that are endemic to French baroque music, and to the grand motet in particular.
In general, this article aims to provide a more detailed and more nuanced account of supposition than has thus far been available by attending not only to Rameau’s own writings but also to the writings of his early critics and to the musical repertories that were these writers’ frame of reference.