This article examines mid-nineteenth-century Anglo-French relations through the prism of musical standardization. Bringing together perspectives from musicology, history of science, and political history, it demonstrates the holistic value of musical practices for the study of processes of political integration. In 1859, Napoléon III's government determined a national pitch to which musicians should tune their instruments. The following year, Britain's Society of Arts attempted to emulate this standard. Amid tense Anglo-French relations, British audiences interpreted the French pitch as a measure of the country's autocracy, and these political anxieties materialized through a redefinition of the standard. The challenges of introducing a musical pitch within a liberal political framework encountered in 1859 were subsequently echoed in debates over the reform of weights and measures following the 1860 free trade treaty between Britain and France. Both the economic and artistic integration of these countries involved the problem of how to regulate society within a laissez-faire state. Musical standardization has received little historiographical attention, but the regulation of this art offers insights into mid-nineteenth-century Anglo-French political culture. Entangled within complex network of industrial, institutional, and social structures, musical pitch demonstrates how problems of economic and social integration were inseparable from international and socio-political contexts.