Sacred music occupies a distinguished place among Beinecke's early books and manuscripts. MS 91, known as the Mellon Chansonnier after its last private owner, Paul Mellon, who presented it to Yale in 1940, is one of the world's most celebrated collections of medieval songs. This beautifully calligraphed manuscript on parchment, Neapolitan in origin and dating from the mid 1470s, may have been prepared for the wedding of Beatrice of Aragon, daughter of the king of Naples, and Mathias Corvinus.
In it are songs by two of the greatest names of medieval music, Johannes Okeghem (ca. 1410-1497) and Guillaume Dufay (d. 1474). A third composer represented in the Mellon Chansonnier is Gilles Joye (ca. 1424-1483).
A facsimile edition with a detailed commentary has been published by L. L. Perkins and H. Garey, The Mellon Chansonnier (New Haven and London, 1979), 2 vols.