Providing source material for liturgical practice on a significant proportion of feast days in each sanctorale cycle, the Commune sanctorum liturgies had crucial daily importance for medieval Christians. Despite their frequent use, or perhaps because of this prosaic nature, the Commune sanctorum has rarely been considered as a liturgical phenomenon in its own right. Focusing on the Old Hispanic liturgy, this article explores the creation and presentation of the Commune sanctorum. We address systematically a question left unexamined in previous scholarship: where did the Commune sanctorum come from? We first survey the Old Hispanic material shared with other rites. Turning then to the Old Hispanic rite’s unique material, we examine materials found only in the Commons and those shared elsewhere in the rite. We set out a methodology for determining the direction of origin for such shared chants, demonstrating the importance of proper saints’ liturgies in the creation of the Commune sanctorum as well as the creative interest in producing new Commons materials. In addition to the origin of the Commune sanctorum, this article engages with manuscript presentation, asking how Commons materials were organized and how such presentations guided liturgical practitioners. A deeper understanding of the Commune sanctorum opens a window onto one of the foundational devotional experiences of Western Christendom.