I posted this video on Fb for the feast of Our Lady of Guadalupe yesterday. It is a hauntingly beautiful piece of polyphony. The words were originally a prayer addressed to our Lady of Guadalupe. In 1599, the then popular prayer was set to music; and now, we are able to hear what this piece sounded like to the ears of Spaniards and natives of New Spain hundreds of years ago!
The words are in the Náhuatl language of the Aztecs. It was found in the oldest (post-conquest) manuscript known to exist. The work lay hidden until 1931, when a priest by the name of Canon Octaviano Valdés discovered it in a small town in Mexico.