“The day in which a High Mass composed by me is performed during the ceremonies solemnized for Your Imperial Highness will be the most glorious day of my life; and God will enlighten me so that my poor talents may contribute to the glorification of that solemn day.” So wrote Beethoven in 1819, upon learning of the future investiture of his patron Archduke Rudolph of Austria as Archbishop of Olmoütz. This would be the starting point for the creation of one of Beethoven’s most notable compositions and one of the most important works in the sacred repertoire.