The founding of the Paris Conservatoire in 1795 was intended to bring standardization and meritocracy to French musical pedagogy. However, major compromises were reached in the setting of the Conservatoire’s curriculum, aimed at synthesizing the diverse pedagogical approaches of its professors. Charles-Simon Catel’s Traité d’Harmonie (1803), the Conservatoire’s official harmony textbook, was one such compromise, written to bring an end to ongoing disagreements between the pro-Rameau and anti-Rameau factions on the institution’s faculty. This paper examines the music-theoretical debates that underpinned the Catel compromise by placing Catel’s Traité in dialogue with the music and pedagogy of composer Henri-Montan Berton. Although largely unknown today, Berton was one of the most prolific opera composers of the Revolution; in 1795, he was appointed harmony professor to the Conservatoire, where he served on the committee which unanimously approved Catel’s treatise. Comparing Berton’s Rameau-inspired conception of harmonic space with Catel’s more pragmatic harmonic doctrine, this paper will present an archaeology of a single chord, the subdominant, tracing its use from Berton’s pedagogical games to his Revolutionary-era operas. This paper argues that the subdominant chord occupied a much more privileged position in Berton’s work than it did in Catel’s Traité d’Harmonie, Berton frequently employing harmonic forms that seem to emphasize the subdominant at the expense of the more powerful dominant. Thus, Berton’s treatment of the subdominant, both in the opera house and in the classroom, reveals just how far Catel’s treatise was removed from the musical practices of the Conservatoire’s faculty.