Although modern scholars have identified copious examples of symbolism in Renaissance sacred music, fifteenth-century treatises on musica practica and speculativa remain conspicuously silent about rhetorical and symbolic devices in contemporary masses and motets. The effect of such theoretical silence is nowhere more resounding than in the masses of Johannes Ockeghem. With some notable exceptions, studies of Ockeghem's music focus largely on the technical aspects of counterpoint in what has become known as Ockeghem’s “aesthetic of concealment.”

This chapter argues that Missa Quinti toni and Missa Prolationum contain symbolism whose inspiration will be found not in music treatises but in the public writings of Nicholas of Cusa and his contemporaries. In particular, these masses reveal devices that correspond with remarkable consistency to the symbolic theologies in Cusa's treatises and public sermons.

Missa Quinti toni proceeds from an apparent chaos of concealed motivic logic, through a plethora of motives elided to their inversion of retrograde inversion, culminating in the first known use of the six voces musicales in incremental form setting the text “qui tollis peccata mundi, miserere nobis”—an explicit musical symbol of Christ as the scala peccatorum. This passage mirrors one of the main theses of Cusa's De quaerendo Deum, that searching for the Lord is like climbing a ladder through the senses heavenward. The expanding canon of Missa Prolationum corresponds closely to theological-geometrical concepts in Cusa's treatise De docta ignorantia, which proves the existence of God through endless expanding geometrical arcs. Most significantly, Cusa argues in De quaerendo Deum that one must search for the Lord by contemplating the Greek name Theos (θϵός). Cusa’s foundational concept appears hidden in plain sight in Ockeghem's Missa Prolationim: the four fundamental musical mensuration signs at the heart of its canon correspond precisely to the four Greek letters of the name of the Lord, imagery echoed in Johann Theodor de Bry's engraving of Hermes Trismegistus, pointing heavenward toward an image that simultaneously represents the four mensuration signs and Theos. Contemporary theology and imagery reveal that this is no coincidence. Ockeghem's masses thus play a central role in documentable traditions of symbolizing divinity as a musical ladder and depicting the name of the Lord in music and visual imagery.