The music of the great liturgies of Antiquity is simply the way the text, as defined by the liturgy, was performed. It was not an optional insertion in the liturgy, and its content was ordained in full by the liturgy. So chant, just like the readings and prayers, was a bearer of the liturgical message. In Eastern Christianity, liturgy and liturgical chant has the task of transmitting the faith itself — most efficiently from the perspective of the congregation. To replace the liturgy and chant was equal to replacing the faith or, at least, of curtailing the faith it conveys; the very beliefs confirmed in the sacred words of the rite. The transmission of the faith must not be weakened. The change to a new language was no more than a change of means, the content still had to be transmitted in its integrity. It was not intended as the “expression of new religious experiments” or the manifestation of the soul of new nations. The “what” — that is above languages and nations — was perfectly defined, the change was only in the “how.”
By contrast, Western chant was given a new function at the end of the Middle Ages. It had to gather and coordinate people, express and invoke private and communal piety, give voice to the affections, or simply provide a background to the liturgy and fill gaps in its procedure. The new approach appears clearly in the idea of “dialogue”: God speaks to the congregation in readings and the sermon, and the congregation answers in singing — differently, of course, according to cultures, languages, historical ages, social strata (or in our time, according to gender, generations, conditions, etc.). By contrast, the old approach regarded the service as a dialogue in every respect: God addresses man in the Word, but man listens to His Word as something already received in the soul, something that is answered by listening to it. And conversely, chant communicates not only the thoughts and feelings of the congregation but it is itself a revelation that combines the divine Word and human resonance. In the liturgy Christ is acting among us, He is Revelation to us, and Prayer for us in every moment of our life. We stand before God in Him, who is Prophet and High Priest in one Person. One view is theocentric and christocentric, and emphasizes the objective, the other is anthropocentric and focuses on the subjective.
St. Benedict provided the formula for the old ecclesiastical view: metis concordet voci. Let us take the words (and chants) on our lips as they are given us by the Church, and form our mind according to the words while singing them. The new approach can be summarized in a paraphrase of St. Benedict’s sentence: vox concordat mentis i. e. let us sing what we feel. As history proves, the two ways should not exclude each other. While taking one of them as a starting point, the other acts as a modifying factor. We express the feelings of the people, while carefully avoiding any conflict with the faith; or: we deal with the objective content of the liturgy, but with regard to human conditions.
Laszlo Dobszay, The Bugnini-Liturgy and the Reform of the Reform (2003)