This book tells three inter-related stories that radically alter our perspective on plainchant reform at the turn of the twentieth century and highlight the value of liturgical music history to our understanding of French government anticlericalism. It offers at once a new history of the rise of the Benedictines of Solesmes to official dominance over Catholic editions of plainchant worldwide, a new optic on the French liturgical publishing industry during a period of international crisis for the publication of plainchant notation, and an exploration of how, both despite and because of official hostility, French Catholics could bend Republican anticlericalism at the highest level to their own ends. The narrative relates how Auguste Pécoul, a former French diplomat and Benedictine novice, masterminded an undercover campaign to aid the Gregorian agenda of the Solesmes monks via French government intervention at the Vatican. His vehicle: trades unionists from within the book industry, whom he mobilized into nationalist protest against Vatican attempts to enshrine a single, contested, and German, version of the musical text as canon law. Yet the political scheming necessitated by Pécoul’s double involvement with Solesmes and the print unions almost spun out of control as his Benedictine contacts struggled with internal division and anticlerical persecution. The results are as musicologically significant for the study of Solesmes as they are instructive for the study of Church-State relations.