From the National Liturgical Week (conference) in 1950

In the Mass as celebrated in 1950, as in the EF now, the priest says the entire Our Father, and the servers respond with the last line only. There are no rubrics for the people. The custom now in most places I've been and heard of is for the people to sing the last line only. There is much talk of people singing the whole Pater Noster (as in many places they say the second set of Domine, non sum dignus with him, or try to), and I think this would be a laudable practice, both for its own sake and for the unity it would bring to the two forms of Mass. I encourage discussion in the comments (if any of you are still reading!).

Father Shawn Sheehan (Cambridge, Mass.): I would like to have Father Ellard tell us what are the official directives on the congregational recitation of the Pater noster.

Father Gerald Ellard (St. Mary's, Kansas): To the best of my knowledge that is an open question. By the analogy that the congregation recites at a Low Mass what it sings at High Mass or answers to the priest, the singing of the Our Father or its recitation by the congregation at a Dialogue Mass would seem to be ruled out. However, all things to the contrary not withstanding, there seems to be a custom in Rome that at High Mass the people sing the Our Father. And I saw a detailed description of two Dialogue Masses in Rome under papal control in which the recitation of the Our Father by the entire congregation was provided for. To the best of my knowledge, there is no prohibition of it, nor is there, beyond this example, any encouragement for it. This is as far as my knowledge goes. I know that there is quite a strong feeling that it would be a good prayer for the people to recite along with the celebrant. I know also that priests have the feeling that this would be a lay encroachment on a clerical privilege, and so I suppose the debate will go on until we have further direction.

Discussion after Gerald Ellard, S.J., "A Brief History of the Dialogue Mass,"
in For Pastors and People: National Liturgical Week 1950, Conception, Mo.: The Liturgical Conference, Inc., 1951, p95.

Note: In a 1963 issue of the journal Worship, a negative response is given to an inquiry about the above, but with the editor's expressed desire that such might change.