ChapterIII-X. Hymns and Other Nonbiblical Songs
173. A very ancient tradition gives hymns the place in the office that they still retain.  By their mystical and poetic character they are specifically designed for God's praise. But they also are an element for the people; in fact more often than the other parts of the office the hymns bring out the proper theme of individual hours or feasts and incline and draw the spirit to a devout celebration. The beauty of their language often adds to this power. Furthermore, in the office hymns are the main poetic element created by the Church.
174. A hymn follows the traditional rule of ending with a doxology, usually addressed to the same divine person as the hymn itself.
175. In the office for Ordinary Time, to ensure variety, a twofold cycle of hymns i~ given for each hour, for use in alternate weeks.
176. In addition, a twofold cycle of hymns has been introduced into the office of readings for Ordinary Time, one for use at night and the other for use during the day.
177. New hymns can be set to traditional melodies of the same rhythm and meter.
178. For vernacular celebration, the conferences of bishops may adapt the Latin hymns to suit the character of their own language and introduce fresh compositions,  provided these are in complete harmony with the spirit of the hour, season, or feast. Great care must be taken not to allow popular songs that have no artistic merit and are not in keeping with the dignity of the liturgy.