The musical tradition of the universal Church is a treasure of
inestimable value, greater even than that of any other art. The main reason for
this pre-eminence is that, as sacred song united to the words, it forms a
necessary or integral part of the solemn liturgy.
Holy Scripture, indeed, has bestowed praise upon sacred song, and the
same may be said of the fathers of the Church and of the Roman pontiffs who in
recent times, led by St. Pius X, have explained more precisely the ministerial
function supplied by sacred music in the service of the Lord.
Therefore sacred music is to be considered the more holy in proportion as it
is more closely connected with the liturgical action, whether it adds delight to
prayer, fosters unity of minds, or confers greater solemnity upon the sacred
rites. But the Church approves of all forms of true art having the needed
qualities, and admits them into divine worship.
Sacrosantum Concilium #112