It contains Gregorian chant settings for the Ordinary of the Mass (Kyrie, Gloria, Credo, Sanctus, and Agnus Dei), comprising a total of eighteen complete polyphonic Masses (and two unfinished ones) by the foremost contemporary composers, among them Jacobus Barbireau, Alexander Agricola, Pierre de la Rue, Marbrianus de Orto, Josquin des Prez, Johannes Ghiselin, and Antoine Brumel.

[1] More recent scholarship attributes part of the codex to calligrapher and music scribe Martin Bourgeois, based on the inscription "hinc Burgos" found within one of the litterae cadassae, and on stylistic similarities to the c. 1504-06 Choirbook of Philip the Fair and Juana of Castile (Royal Library of Belgium, MS 9126), which has been attributed to him.

[1] It is known that the manuscript was commissioned by Manuel I of Portugal on the occasion of his second marriage, to Maria of Aragon, daughter of the Catholic Monarchs, in 1500.

[1] The king was a noted music-lover, as detailed in the chronicles of Damião de Góis.

[4] The Gradual was left to the king's daughter, Isabella of Portugal, the wife of Charles V, Holy Roman Emperor, thus explaining its incorporation into the Imperial Court Library (precursor of the modern Austrian National Library).