ChapterIII-III. Ways of Singing the Psalms
121. Different psalms may be sung in different ways for a fuller grasp of their spiritual meaning and beauty. The choice of ways is dictated by the literary genre or length of each psalm, by the language used, whether Latin or the vernacular, and especially by the kind of celebration, whether individual, with a group, or with a congregation. The reason for using psalms is not the establishment of a fixed amount of prayer but their own variety and the character proper to each.
122. The psalms are sung or said in one of three ways, according to the different usages established in tradition or experience: directly (in diredum), that is, all sing the entire psalm, or antiphonally, that is, two choirs or sections of the congregation sing alternate verses or strophes, or responsorially.
123. At the beginning of each psalm its own antiphon is always to be recited, as noted in nos. 113-120. At the end of the psalm the practice of concluding with the Glory to the Father and As it was in the beginning is retained. This is the fitting conclusion endorsed by tradition and it gives to Old Testament prayer a note of praise and a Christological and Trinitarian sense. The antiphon may be repeated at the end of the psalm.
124. When longer psalms occur, sections are marked in the psalter that divide the parts in such a way as to keep the threefold structure of the hour; but great care has been taken not to distort the meaning of the psalm.
It is useful to observe this division, especially in a choral celebration in Latin; the Glory to the Father is added at the end of each section.
It is permissible, however, either to keep this traditional way or to pause between the different sections of the same psalm or to recite the whole psalm and its antiphon as a single unit without a break.
125. In addition, when the literary genre of a psalm suggests it, the divisions into strophes are marked in order that, especially when the psalm is sung in the vernacular, the antiphons may be repeated after each strophe; in this case the Glory to the Father need be said only at the end of the psalm.