The Dominican friar Johannes Nider (1380–1438), known today as the father of witchcraft literature, played an important role at the Council of Basel (1431–49) on the Council's delegation to the Hussites and its deputation on religious reform. Despite Nider's reputation as a reformer of religious communities, his approach to communal liturgy has not attracted close attention. This article focuses on his broad theoretical treatise, De reformatione religiosorum or De reformatione status cenobitici (On the Reform of the Religious State), in which Nider articulates a philosophical concept of reform as the restoration of beauty, manifested in well-ordered and balanced proportion. In the interest of universal applicability, the treatise remains abstract. However, biographical descriptions of Nider from his contemporaries and the visitation letters he wrote to women's convents show Nider as an engaged liturgical leader, a talented singer with a robust voice, and a zealous expert in the legal particulars of Dominican liturgical regulations. In light of these contexts, De reformatione's sweeping laments over liturgical neglect and academic metaphors of well-disposed proportion are not just rule-hammering and scholastic fancy but rather universalized expressions of Nider's lived commitment to Dominican musical and ritual practice.

Liturgy has often served as a source for studying the identities of medieval religious communities through examining local saints and special chants or ceremonies. This article deepens such approaches by considering the practice of liturgical coordination, which required each convent to reconcile the obligations imposed upon it by the order to which it belonged, the diocese in which it lay, and the personal networks of its sisters. The shifting dates of the Easter cycle created a wide variety of possible calendrical conflicts and necessitated that each convent's liturgical practice be organized anew every year. Focusing on German-language liturgical manuals from Observant Dominican convents, this article introduces these sources and examines the various obligations, authorities, and sources of advice that Dominican sisters coordinated when planning each year's liturgy. It then turns to the concrete example of a major calendrical conflict on May 1, 1519, which illustrates how convents negotiated their networked obligations and defended their decisions. Supplementing traditional sources such as chronicles and charters, liturgical administrative documents reveal how each convent's liturgical identity was both iterative and networked and how the tensions between these features opened up spaces for assertive decision-making.