The psalms were central to the medieval liturgy and constituted the core of the Divine Office. Clergy had to know all the psalms from memory. Psalters contain the texts of the Psalms in Latin translation, either as a section of a larger book for the Divine Office or in a separate volume. In addition to the psalms, a ferial psalter contained the items of the Divine Office that did not change from day to day, often including the invitatories, antiphons canticles, chapters, short responsories, hymns, and litanies.
In manuscripts, the psalms were usually divided into groups, each beginning with a major decorated initial. The simplest division into three groups (beginning with psalms 1, 51, 101) is found in early psalters from Ireland and Germany. A five-part division (groups beginning with psalms 1, 41, 72, 89, and 106) is rare. The most common is the eight-part division, with major initials for psalms 1, 26, 38, 52, 68, 80, 97, and 109. These divisions correspond to the groupings of psalms in the Divine Office on successive days of the week in non-monastic churches: psalm 1 was the first psalm of Matins on Sunday, psalm 26 on Monday, psalm 38 on Tuesday, and so on through Saturday. Psalm 109 was the first psalm sung at Sunday vespers. (Monastic and secular uses differed somewhat in their distribution of the psalms over the course of the day and week.)
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 (antiphoner 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 antiphoners. 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.
An Office lectionary contains readings for the Office of Matins (also called Nocturns). Medieval Matins services consisted of two or three nocturns (not to be confused with the other name for Matins) that included recited lessons followed by sung responsories. Matins on important feasts and Sundays had three nocturns, while less important feasts and weekdays had only two nocturns. The lessons of the first nocturn were drawn from the Bible, those of the second nocturn from hagiographic or patristic texts, and those of the third nocturn from patristic commentaries on scripture, often taken from a homiliary. The number of lessons in each nocturn varied. On a weekday in winter or a minor feast, a nocturn might contain only a single lesson. On a major feast or on a Sunday, each nocturn would have 3 lessons (in cathedrals) or 4 lessons (in monasteries). Lectionaries follow the order of feasts in the liturgical year. Office lectionaries became less common after the development of the breviary beginning in the twelfth century.
A legendary contains the lives of the saints celebrated in the liturgy. The book’s name derives from the Latin legenda (“things to be read”). The legendary could be a source of the hagiographic texts recited in the second nocturn of Matins. Legendaries vary widely in their selection of saints and of texts. While their contents may vary, their order normally follows that of the liturgical year.
A homiliary contains homilies on the Gospel readings of the day. They were the sermons delivered, often by the bishop, in late antiquity and the early Middle Ages at Mass. Excerpts from these texts were read in the third nocturn of Matins.