Debates concerning the appropriate nature of sacred music in France persisted throughout the nineteenth century. While many figures within the Catholic Church took the more traditional stance in their proclamation of plainchant as the genre of sacred music par excellence, other priests and church musicians insisted that more modern styles of composition were not only appropriate but necessary for French Catholics. This debate was not limited to the confines of the Church: Republican composers, for their part, also contributed their views on the matter, which largely stated that the realms of sacred and secular were not mutually exclusive. This chapter outlines the debate on both sides in order to reveal how Republican composers absorbed the numerous criteria involved in the composition of sacred music into their secular constructions of French music. It also reveals the discursive slippages between Catholic denigrations of “modern” religious music and “secular” compositional styles: more often than not, modern religious music was strikingly close to the Catholic ideal, even when it was written by a decidedly secular composer for non-liturgical use. A study of Contes mystiques, a collection of twelve mélodies written by such composers as Gabriel Fauré, Théodore Dubois, Henri Maréchal, and Pauline Viardot, reveals how Republican composers absorbed the numerous criteria involved in the composition of sacred music and how this modern music was strikingly similar to the Catholic ideal, even when written by “secular” composers for non-liturgical use.