In the upper-right-hand corner of the Panis Angelicus that we've been singing appear the initials "N.A.M." In fact, you'll find those initials all over the abridged St. Gregory Hymnal and Catholic Choir Book that some of us still have. They stand for Nicola Aloysius Montani, and the Adoremus website has a fascinating article written by Lucy Carroll about him: "Nicola A. Montani and the Catholic Liturgical Revival of the Early 20th Century."
Montani founded the Society of St. Gregory and the St. Gregory Guild. More than a century ago, Montani took it upon himself to execute Pope Pius X's motu proprio, Tra le sollecitudini; Instruction on Sacred Music, which deserves a read of its own. Nice to know ours is not the only era in which chant and polyphony have taken a back seat in the liturgy.
Carroll points out Montani was something of an iconoclast as he excised the profane and restored the sacred in liturgical music. If Montani had had his way, the Schubert Ave Maria would be placed in the same category as the Mendelssohn Wedding March as inappropriate for Mass. What Montani did accomplish was to rearrange many classic polyphony pieces to make them more accessible for choirs...which Pius said should only consist of men and boys. Considering how difficult it has been for us to recruit basses, I'm glad that restriction is long gone. (ETA: So, obviously, are the sopranos and altos!)