The early-16th-century manuscript commonly known as the Geese Book (New York, Morgan Library, M. 905) contains the entire Mass liturgy sung by the boys choir of the parish church of St. Lorenz in Nuremberg, Germany prior to the Reformation. This thesis addresses the location and function of the sometimes enigmatic marginalia and the decorated or historiated initials in this large two-volume gradual. The paper begins with an analytical case study of a scene within the margins in which a wild woman, wielding a club, confronts a female dragon who has taken a child. Subsequently the size, subject matter, and physical positioning of the illuminations and decorations within the book and on its pages are examined with respect to the gradual's liturgical contents. It is hoped that through such methods, new conversations may begin as to the roles that marginalia and decoration may play within the multiple organizational schemes within a musical text of this kind.