91 So that it may really be possible in practice to observe the course of the hours proposed in Art. 89, the psalms are no longer to be distributed throughout one week, but through some longer period of time. The work of revising the psalter, already happily begun, is to be finished as soon as possible, and is to take into account the style of Christian Latin, the liturgical use of psalms, also when sung, and the entire tradition of the Latin Church.
Source: Sacrosanctum Concilium (Vatican.va)