The gradual contains the sung portions of the Mass, particularly the chants for feasts, Sundays, and the common of saints. In each Mass several chants were “proper” to the occasion (introit, gradual, sequence, alleluia (replaced by a Tract in penitential seasons), offertory, and communion). The ordinary chants were those sung at every Mass (Kyrie, Gloria Credo, Sanctus, Agnus Dei, and Ite Missa Est). While the melodies of the ordinary chants varied, their texts did not, except through the addition of tropes (poetic interpolations). Graduals from the high and late Middle Ages may incorporate material that earlier was contained in separate books or sections: the kyriale (containing choir chants of the Ordinary of the Mass), the cantatorium (a book for soloists, containing the gradual and Alleluia, the solo chants of the Proper), the earlier type of gradual (containing choral chants of the Proper), the sequentiary or proser (containing sequences, also called proses) and the troper (containing troped versions of various chants).
Processions took place before the principal Mass every Sunday and on important feasts, although other processions could occur at the end of Lauds and Vespers of the Office, especially during the octaves of Christmas and Easter, or to a particular altar on a saint’s feast. Usages with regard to processions varied from place to place. Processions on Palm Sunday, for instance, were unique to each church and could be particularly elaborate, often involving movement around a city or town to reenact Christ’s entry into Jerusalem. Directions for some processions can be found in a missal; the most extensive information appears in an ordinal. The chants for a procession were proper to the feast.
A processional contains the chants sung during the processions on certain important feasts of the church year, including Christmas, the Purification of the Virgin Mary, or Candlemas (February 2), Ash Wednesday, the Adoration of the Cross on Good Friday, the major litanies (April 25) and Rogations (during three days before the feast of the Ascension). Processionals began as small booklets of chants in the tenth and eleventh centuries, but gradually developed into separate books, while retaining their small size for portability.