Medieval Chant for the Mass Ordinary

The Ordinary of the Mass (Lat.: ordinarium missae) is part of the Roman mass and comprises six chants whose texts remain the same through the year, namely Kyrie eleison, Gloria in excelsis Deo, Credo, Sanctus, Agnus Dei, and Ite, missa est. An initial repertory of these chants were established by the end of the first millenium, but compositions of new monophonic chants or full cycles along with polyphonic elaborations of older chant repertories continued up to the Early Modern period. While the texts of these chants did not change (although there are some exceptions), interpolations in the form of tropes (newly composed texts with music inserted before and between the phrases of established chants) or prosulas (newly composed texts underlaid to preexistent melodies) were cultivated from the 9th century on. The full scope of the repertory is still unknown; present catalogues count around two thousand melodies, but some of them were used for more than one chant in the group (most typically Sanctus and Agnus Dei or Kyrie eleison and Ite, missa est) or, in particular in the late Middle Ages, adapted from other genres. There was never a unified repertory of chants of the mass ordinary for the whole Western church, but individual regions (Spain, Central Europe, etc.), religious orders (Cistercians), or dioceses developed their own traditions. Melodies of the mass ordinary chants often had their own character, employing, among other elements, repetitions of short melodic formulas or, typically in the late period, moving in the modus mixtus (authentic and plagal range of one mode) and introducing rhythmized sections (cantus fractus).