21 Certainly no one will be astonished that the Church is so vigilant and careful about sacred music. It is not a case of drawing up laws of aesthetics or technical rules that apply to the subject of music. It is the intention of the Church, however, to protect sacred music against anything that might lessen its dignity, since it is called upon to take part in something as important as divine worship.
Source: Musicae Sacrae (Vatican.va)