Missa Papae Marcelli, or Pope Marcellus Mass, is a mass by Giovanni Pierluigi da Palestrina. It is his most well-known and most often-performed mass, and is frequently taught in university courses on music. It was always[citation needed] sung at the Papal Coronation Mass (the last being the coronation of Paul VI in 1963). The Missa Papae Marcelli consists, like most Renaissance masses, of a Kyrie, Gloria, Credo, Sanctus/Benedictus, and Agnus Dei, though the third part of the Agnus Dei is a separate movement (designated "Agnus II").The mass is freely composed, not based upon a cantus firmus or parody. Perhaps because of this, the mass is not as thematically consistent as Palestrina's masses based on models. It is primarily a six-voice mass, but voice combinations are varied throughout the piece; Palestrina scores Agnus II for seven voices, and the use of the full forces is reserved for specific climactic portions in the text. It is set primarily in a homorhythmic, declamatory style, with little overlapping of text and a general preference for block chords such that the text can clearly be heard in performance, unlike many polyphonic masses of the 16th century. As in much of Palestrina's contrapuntal work, voices move primarily in stepwise motion, and the voice leading strictly follows the rules of the diatonic modes codified by theorist Gioseffo Zarlino.