Following the conquest of Mexico by Cortes and much of Central America by Alvarado, cathedral churches were established throughout the region, all with European-style polyphonic choirs. Among the most important of these early centres of Spanish culture was the cathedral of Guatemala City, where polyphony was already in use in the 1540s. Shortly after 1600, the organist and choir director of the cathedral collected, organized, and copied into choirbooks all of the music used by the choir. The manuscript presented here in modern edition, one of at least five choirbooks prepared at the time, contains a number of otherwise unknown works by such major Old World composers as Francisco Guerrero and Cristobal de Morales. Significant works by Hernando Franco and Pedro Bermudez, choirmasters of the Guatemala City Cathedral, are also included. The manuscript presents a unified repertory for Holy Week and for the Salve services in Lent, including four settings of the Passion, for which the Spanish were famous throughout Christendom. Some of the works predate the 16th-century reform of the Roman Breviary and Missal, among them the original versions of several Vespers hymns and Magnificat settings by Guerrero that are otherwise known only in later versions found in Spanish sources. An introduction discusses the formation of the cathedral's musical repertory and illuminates both Old and New World practices of 16th-century Spanish liturgical music.