This Sunday is the Second Sunday of Easter, sometimes called Low Sunday and sometimes called, after the first words of the Introit, Quasi modo Sunday
This beautiful and unforgettable song is dedicated to first communicants (children or new converts), an instruction about how to proceed and growth in faith. It is especially compelling to us because of our literary and pop-culture knowledge of the bell ringer in "Hunchback." It is good know the original meaning and idea -- and also to sing the real song as the Introit at Mass.
What does this Introit say to and about first communicants? It says nothing about their need to go on a rampage against error or laxity among the other faithful; instead it counsels the first communicant or the convert, likened to a newborn child, to desire the milk of the mother, to receive that nourishment and grow. Properly disposed, the new communicant doesn't need to be told this. But the rest of us sing about this as a reminder that there are children among us who need to be cared for, and that we all should preserve the spirit of the children of God and remain humble and submissive to the Divine Will.
Musical commentary from Johner: "The song is extremely simple, almost naive. After it has risen to the tonic of the sixth mode (f), it clings to it as if in fear. It moves about this note, several times descends lower, but always strives toward it against. This is especially shown with infantes, al-(leluia). The plagal form of the F mode could scarcely be evidenced more clearly. Melodically, rationabiles, with its harmonious line, is the highest point of the song. Its constituent notes are but a syllabic part of the psalm-verse of the Introit: adjutori nostro. The Introit for the vigil of Christmas resembles this melody to some extent. After sine dolo there is a sort of break.... Of the three alleluia the second forms a single note. After the preceding d, the first sets in on c, while the third sets in on d after the preceding c; thus the beginnings are pleasantly varied."