"Bernardino de Sahagún\&##39;s Psalmodia Christiana and Catholic Formation Among the Mexica in Sixteenth-Century New Spain." In 1583, Pedro Ocharte published the first book of vernacular sacred song in the Americas--the Psalmodia Christiana by Bernardino de Sahagún. Its 333 songs composed in the Nahuatl language sought to promote the formation of Catholic communities among the Mexica (commonly known as the "Aztecs"). This lecture highlights the legacy of Western plainchant traditions in the Christian evangelization of the New World and shows how Mexica sacred music traditions were folded into the European thrust of the Christian mission in sixteenth-century New Spain.