The Proper chants are imbued with a special kind of poetical power, which is lacking in strophic poetry, even in its most wonderful hymns. The chants of the Proper announce the great truths of Christian doctrine and liturgical theology, in most instances without direct didactic persuasion, and without decorating the teaching with lyrical ornaments. They are “poetical” by speaking with the vocabulary of the Bible, i.e. with adapted words. In a certain sense they resemble similes, chiefly when they quote from the Old Testament. The theological truths are transmitted, and yet — concealed in their intimacy. Simple words and images are, as it were, dropped into the mind of the listener, where they come to light; figurative speech becomes reality in prayerful silence. An authoritative expert in aesthetics has explained that the essence of great poetry is an enigmatic oscillation between layers of meaning, and between the temporal “reference points” (that is past, present and future) in a poem. This same oscillation is present in the liturgy not as an outcome of creative will, but in virtue of Divine Providence: the same Poet, God Himself, pronounced the Old Testament, uttered the Good News, and fulfilled (still fulfills) both in the sanctified life of the Church. When we sing a Proprium chant, we always think (or at least we feel or sense) more than is actually delivered by voice and lips. We surmise the fulfillment itself in the words, and therefore they are the words of the heavenly liturgy. This tactful, discreet poetry is hardly attainable by the plain language of ecclesiastical poetry. […]
With this in mind, I ask once more: where is the “alius cantus” [“anything else that is appropriate”] that is able to speak with such strength, such theological profundity, such poetic intimacy, but also with such simplicity, of the Paschal mystery? With what majesty does the celebration of Easter rise up out of the silent depths of this personal (and mystical) dialogue! And how powerful the pedagogical effect of this poetry which teaches us to regard our religion primarily as a very personal union with God, and not merely as adherence to a group of people, as it were, to a party or some “community.” We learn to seek this inner truth without despising the external form that delivers the inner meaning. It is enough to read (or better: to sing) the daily Introit chants of the Easter octave to see how the Mystery, with its many dimensions, unfolds in the Church’s chant.
Laszlo Dobszay, The Bugnini-Liturgy and the Reform of the Reform (2003)