I noticed he re-released it yesterday. The Pope also published a list of Vatican II documents that the laity should be familiar with, which didn’t include Musica Sacra, but it did include other documents that weren’t particularly relevant to the laity (ie: on the priesthood, sacred liturgy). Perhaps this was his way of subtly letting the laity (including OCP) know what Vatican II said about sacred music now that the Pope is bringing up Vatican II again.
Musicam Sacram came out in 1967, after the Council had concluded. It was (is) an instruction based on the Constitution on the Sacred Liturgy, but not one of the documents of VII itself.
To participate in the discussions on Catholic church music, sign in or register as a forum member, The forum is a project of the Church Music Association of America.