18 The Sovereign Pontiffs have always diligently fulfilled their obligation to be vigilant in this matter. The Council of Trent also forbids "those musical works in which something lascivious or impure is mixed with organ music or singing." In addition, not to mention numerous other Sovereign Pontiffs, Our predecessor Benedict XIV of happy memory in an encyclical letter dated February 19, 1749, which prepared for a Holy Year and was outstanding for its great learning and abundance of proofs, particularly urged Bishops to firmly forbid the illicit and immoderate elements which had arrogantly been inserted into sacred music.
Source: Musicae Sacrae (Vatican.va)