Here is an interesting article
Although the Council stated that the “Church acknowledges Gregorian chant as proper to the Roman liturgy” and that it should have the principal place in liturgical services, there followed a “widespread abandonment of Latin and Gregorian chant.” This laying aside of the Roman rite’s own music caused Pope Paul VI in 1974 to issue a booklet containing the easy and familiar chants with a request that at least these would be taught to the faithful. He sent this booklet to all the bishops and heads of religious orders in the world in the hope that the study and practice of Gregorian chant would be promoted. He had hoped for a new springtime by means of the liturgical renewal which would be “the fruit of that seed which Dom Guéranger worked to scatter. This loss of interest in Latin and Gregorian chant was due to the changes in the liturgy with its complete translation and use in the vernacular languages. The chants were available in Latin only, so that when the liturgy was employed in the vernacular the chant books were relegated to the library shelves and other music was adopted which was in the language of the people and could be more easily used by those not trained in chant. Besides this, the melodies of the chant were fitted for the Latin language and any translation of the sacred texts also required a corresponding adjustment to the chant so as to accommodate the difference in accent and syllabic structure. This disuse of Gregorian chant is occurring still today, even though it has been strongly affirmed in the post-conciliar documents and “the desire is repeatedly stated that chant is to be preserved in the reformed liturgy.
There needs to be renewed in the Church the liturgical movement founded by Dom Guéranger, because it has not yet been completed. Once again the sacred chants should be heard at Sunday Mass in parishes throughout the world, so as to move them spiritually and allow them to draw deeper into the interior life. This liturgical movement that followed the secularization of the French Revolution and was a means to reestablish the Christian sentiment in society is as much needed now as it was then. Pope Pius XI spoke of this when he said that the “liturgical chant played no small part in converting many barbarians to Christianity and civilization,” and that it was due to these chants “that St. Augustine made up his mind to become a Christian.” In our own day, when the secularization of society is not just on a national level but has spread to whole continents, there needs to be a deep spiritual renewal. This can be brought about by the renewal of the liturgical life in parishes as well as by the home being the domestic Church where the fruits of the liturgy are implanted in the souls of future generations. Living the liturgical year helps us in understanding the truths of the Faith in such a way that our faith is “enlightened more and more each year” while a theological sense is formed within us and the brightness of the mysteries “becomes so vivid that the mind and heart are enthralled” and “we begin to grasp the joy that the eternal sight of these beautiful and divine realities will give us.”