One final note on this for now. In 1969, a question was sent to Rome asking if the permission to use hymns in Mass (which was granted in 1958) still applied. The answer was as follows:
That rule has been superseded. What must be sung is the Mass, its Ordinary and Proper, not ‘something,’ no matter how consistent, that is imposed on the Mass. Because the liturgical service is one, it has only one countenance, one motif, one voice, the voice of the Church. To continue to replace the text of the Mass being celebrated with motets that are reverent and devout, yet out of keeping with the Mass of the day amounts to continuing an unacceptable ambiguity: it is to cheat the people. Liturgical song involves not mere melody, but words, text, thought and the sentiments that the poetry and music contain. Thus texts must be those of the Mass, not others, and singing means singing the Mass not just singing during Mass.
(Notitiae 5  page 406)
When the USCCB (the Bishops in these USA) were asked the same question in 1993, their response was to quote the above paragraph. Nothing has changed in the rules, just in the practice of some parishes. Let us be obedient and do what the Church tells us to; always seeking to display the full glory of God.