The Office

Unlike the Mass (which is a single occurrence, although repeatable throughout the day), the Office structures multiple sessions of prayer at set hours during the day. Also, unlike the Mass which can be traced to direct institution by Christ, the Office has its origins in more generalized directions for continuous and watchful prayer (e.g., Ps. 119:164, Mark 13:34-35, Luke 11:2-4, 1 Thess. 5:17), which derive from the Jewish tradition of community prayer in the synagogue at specific times during the day. As learned from the Jewish custom, these prayers were at first only for the opening and closing hours of the day; gradually other fixed or "canonical" hours were added, and the final form was established by Benedict of Nursia in the first half of the 6th century. Benedict's Rule lays out very clearly the times and order of daily prayer, including recitation of the entire psalter over the course of the week; the Rule also specifies readings from scriptural and patristic texts at Matins. Since monks were responsible for the running of Rome's churches during this and the following century, the monastic office came to form the basis also for the secular office. These two uses, monastic and secular, remained the basis for daily prayer in the Western church throughout the Middle Ages, although --as one would expect-- with considerable local and seasonal variation.

As originated by Benedict, the office would occupy some four to five hours of a monk's day; with gradual and sometimes intense elaboration, the daily office at one point grew to where it was absorbing an astonishing ten to twelve hours, especially on the most important feasts. Reform of the Office was, obviously, a frequent refrain in those orders who split away from traditional Benedictine monasticism.

The eight services, with a highly simplified outline of their times (which would have varied according to local custom, as well as geographical and seasonal determination of the amount of daylight available):

Matins 2:30 am
Lauds 5:00
Prime 6:00
Terce 9:00 (the daily Mass usually took place after Terce)
Sext noon
None 3:00 pm
Vespers 4:30
Compline 6:00

 A breviary unites all the chants and texts needed for the celebration of the Divine Office. It combines the separate books that contained prayers (the collectar), Matins lessons (the office lectionary), chants (antiphonal and choir psalter), and ordinary chants and readings (the diurnal). The individual texts may be indicated only by their incipit. Breviaries are often small portable books, usually smaller than antiphonals. Breviaries meant for use in choir can contain musical notation , but those for private recitation of the Office, which was increasingly common in the later Middle Ages, are not notated. Some luxurious breviaries are fancifully decorated but many are modest books devoid of illumination .

Smith Western MS 16, f. 116v:A breviary from 12th century Auvergne. Med/Ren Frag. 24, f. 1: A breviary from 13th century Flanders.
Med/Ren Frag. 09, recto:A breviary from 15th century northern Italy. General MS143An orational for the office, produced by stencil in France in 1779.