IV. Singing the Divine Office
37. Celebration of the divine office in song is more in keeping with the nature of this prayer and a sign of both higher solemnity and closer union of hearts in praising God. In keeping with the explicit wish of the Constitution on the Liturgy,  therefore, the singing of the office is strongly recommended to those who carry it out in choir or in common.
At least on Sundays and holydays it would be well for them to sing some part of the office, especially morning prayer and evening prayer, the two principal hours.
Other clerics living together in centers of study or coming together for retreats or for other meetings should take the opportunity to sanctify their assemblies through the singing of some parts of the divine office.
38. In the singing of the divine office both the law in force for those bound to choir and particular indults remain unchanged. But the principle of "progressive" solemnity is applicable; namely, the parts that of their nature are more directly designed for singing (dialogues, hymns, verses, canticles) are sung and the other parts recited.
39. The faithful are to be invited, and also instructed through proper catechesis, to celebrate some parts of the divine office together on Sundays and holydays, especially evening prayer or whatever other hours are customary in different places or groups. All the faithful, especially the better educated, are to be guided through proper instruction to use the psalms in their Christian meaning for prayer. In this way the faithful will be led gradually to a fuller appreciation and use of the Church's public prayer.
40. Formation in the use of the psalms is particularly important for members of institutes professing the evangelical counsels, in order that they may posses a rich resource for nurturing their spiritual life. They should, if possible, celebrate the principal hours of the office, and even with singing, so that they will take part more completely in the public prayer of the Church.
41. Clerics must retain Latin in the choral celebration if the office, in conformity with the norm of the Constitution on the Liturgy that is based on the centuries-old tradition of the Latin rite. 
The Constitution on the Liturgy,  however, also makes provisions for the faithful, nuns, and other nonclerical members of institutes professing the evangelical counsels to use the vernacular in the office. Attention should therefore be given to providing melodies for the vernacular singing of the divine office.