This study examines painted leaves and fragments that were extracted from a set of choir books created in the last decade of the fifteenth century for the basilica of Santa Maria in Aracoeli in Rome. These remnants are currently housed within various library and museum collections throughout Europe and the United States. The set is agreed upon generally by scholars to have been commissioned by Alexander VI (Rodrigo Borgia, 1431-1503), who was pope from 1492 to 1503, as a gift to the church during his time as pontiff. The choir books for Santa Maria in Aracoeli contain the bulk of the known body of work by the enigmatic illuminator Fra Antonio da Monza. The best known items from this set of choir books are a complete gradual (or book of chants for the Mass) currently housed in the Getty Museum, called the Ludwig Aracoeli Manuscript, and a montage of cuttings in the Albertina Museum, Vienna, that features a miniature of the Pentecost. These are studied in the context of the artistic patronage of Alexander VI, and political and diplomatic gift cultures in papal Rome during the last decade of the Quattrocento. Alexander VI's gift to Santa Maria in Aracoeli served multiple functions. It advanced church music, but is also an example of a pontiff using custom luxury books for cultural diplomacy. The intent of the choir books was to build social relationships and augment the prestige of Alexander VI's regime with a local audience. Alexander VI sought to acknowledge the symbolic resonance of Santa Maria in Aracoeli and attempted to recuperate the site's importance for his reign through the gift. This study argues that the choir books were commissioned by the pontiff to promote his cultural and religious authority through abbellimento or "embellishment", the practice of commissioning ostentatious liturgical objects and additions to religious ceremonies for the purpose of developing esteem for an ecclesiastical office. This thesis argues that another purpose of the bestowment was to appease the Observant Franciscans in charge of the basilica in anticipation of Alexander VI's reforms of the Franciscan order.