The document What is a Catholic Hymn? is written as though only the Mass is relevant. No hymn written before 1963 was intended for use at Mass, most were for devotions, school assemblies, etc., perhaps for the Office. And indeed hymns are now generally not needed for Mass, but are for the Liturgy of the Hours.

Various types of religious songs (carols, noels, cantigas, laude, Leisen, etc.) have existed in the Catholic sphere since the Middle Ages, but, as noted above, they were mostly sung outside of Mass. In the 19th century the Caecilian movement in German-speaking lands promoted the Singmesse or Betsingmesse, in which the faithful sang hymns in the vernacular that paraphrased what was happening at the altar. J.B. Singenberger and his son Otto were two (among many others) who brought the Singmesse and German hymns to the United States, for example: "Grosser Gott" (Holy God, we praise Thy name), "Gott Vater, sei gepriesen" (God Father, praise and glory) or "Freu dich, du Himmelskönigin" (Be joyful, Mary, heavenly Queen). I must admit ignorance as to whether hymns like these were actually sung at Mass (as opposed to other events) before the mid-20th century; others may know more. Fr. Anthony Ruff has written on this topic.

Pope PIus XII mentioned the singing of popular hymns in the vernacular "wherever ancient or immemorial custom permits" in his 1958 Instruction, De musica sacra et sacra liturgia, article 14 a & b. However, he specified that this may be done after the sacred words have been sung in Latin (italics mine). Also, the places where this was an ancient or immemorial custom was probably not the average parish in the United States at that time.

"My concern is the lived experience of ordinary parishes, where hymns quietly form belief week after week."

I started to write a very long reply about my coming into the Church 26 years ago and what I have experienced since then as a musician in both English and Spanish-speaking parishes. But my story was way too long and I realized that it could be summarized in a few thoughts:

a) YES, the music totally affected me, right from the beginning, as a new Catholic.

b) NO, it did not "quietly form (my) belief" because I was influenced also very much by Mother Angelica, who was very traditional; and also by my general affinity for tradition and order.

c) In the midst of it all, God calls us to a deeper understanding, so eventually some of us wake up and know something isn't right at Novus Ordo Masses with modern music.

d) I discovered the Latin Mass 19 years after I came into the Church, and it changed everything for me.

e) My mission since 2019 is to try to "fix" the music in whichever Novus Ordo parish I am serving, and to try to (gently) educate other musicians/parishioners about the rubrics which govern the Mass, while continuing to study on my own.

f) A portion of Novus Ordo parishioners really long for traditional Mass and traditional music. A portion of them detest anything traditional. Some say they HATE Latin.

g) For people who are not seeking to deepen their faith, the modern music IS the Mass.

h) They did a great job in the 70s and 80s of ruining the Mass by simply changing the music. Everything else fell into place after that.

Hymns in the English language were certainly used and sung at the low Mass prior to 1965 or so. I started first grade in Catholic parochial school in 1955 and graduated from the eight grade of the same school in 1963. Starting in fourth grade, the students from the school would sing English hymns at Sunday Mass. The congregation could join in, of course. For the most part, these hymns came from St. Basil's Hymnal, Sunday School Hymn Book, and Our Lady of Mercy Hymnal. We had so-called hymn cards (as many parishes did) comprised of 15 or so "favorite" hymns. Needless to say, we also sang hymns of this genre in school (morning and afternoon) and at various para-liturgical services. Seasonal hymns were important; for example, for the Feast of Christ the King, we would always sing "An Army of Youth" (for Christ the King by Daniel Lord, S.J.) Many of these fine hymns of the faith can be found in A CATHOLIC BOOK OF HYMNS, 2021, Sacred Music Library.

THE HOLY CROSS HYMNAL (with Words and Music by Cardinal O'Connell) was first published in 1915 and continued to be marketed by McLaughlin & Reilly Co., of Boston up until the time of Vatican II. On the opening page is a recommendation by Cardinal O'Connell: "A good method of using these Hymns for devotion at Mass is the following:
Before Mass--Hymn to the Holy Trinity or Holy Spirit
Beginning of Mass--Hymn of Holy Mass
After Consecration--The Blessed Sacrament (a favorite of mine)
At Communion--Holy Communion
At the Blessing--Hymn for the Blessing
Between the beginning of Mass and the consecration may be sung a Hymn: to the Blessed Virgin Mary, St. Joseph, Sacred Heart, or Guardian Angel, or any other hymn appropriate to the day."

So, as you can see, English hymns at Mass were not really a post-Vatican invention, although since 1970 or so the four-hymn sandwich predominates in most parishes. Occasionally, I like to attend a Sunday Mass without any music; but they are hard to find.

Thanks, Roborgelmeister, for mentioning the Ave Maria Hymnal by Rev. Joseph Pierron, who was director of music at Boys Town, Nebraska, and was also editor of CAECILIA in 1930. I checked my two editions (1929 and 1941), and I see that Father Pierron, like Cardinal O'Connell, recommends certain English hymns for use at Communion, after Communion, and so forth. This is an outstanding hymnal.