During the preaching of parish missions the Oblates aimed at maximum involvement by the people. Singing was one of them, but with certain conditions:
In the missions. I recommend you use hymns with a refrain, which the congregation can repeat. I insist that there be refrains which the whole congregation can sing, nothing more.
I don’t find anything more wearisome than listening to some isolated voices which annoy you by their unison without anyone being able to hear one word of what they utter. It is the very opposite of devotion. In this case, music, far from sending the souls to God, turns them away from him. Instead of praying at such a precious moment, people languish. People prefer to pray fervently without being distracted by the singing.
And so I would like to suppress, in our missions, any adoration, any hymn, in which the refrain could not be repeated by the entire congregation. Hence I insist on hymns with a refrain because during the mission all must sing.
Letter to Jean Baptiste Mille, 6 April 1837, EO IX n 611