Propers in the Mass
Making a case for using the propers of the Mass.
I've always reduced it to a very simple argument. If the Church has chosen this for the particular day, what makes you think your judgement is better than the Church's in choosing a hymn?
I know the Gregorian Chants are difficult. So here's my solution. Use Psalm tones to the english translation. I have tried with youths a few years younger than me. Using Sunday Compline, I spent some time pointing the Psalms and Canticle, made up the music for some parts, and taught my peers at a retreat. The Antiphons were sung to psalm tones also. They took to it like fish to water.