The greatest change has taken place in an area which has not been specified by any provision of the Constitution, namely in the position of the hymn within the Hour. The rule which was followed without exception by hundreds of liturgies of dioceses and religious orders, and by the most varied branches of the Office of the Roman liturgy, had already been reflected in the Rule of St. Benedict, which provides the earliest existing detailed account of the Roman Office, namely that the hymn is to be sung before the canticle (though separated from it by a versicle) in the three Hours (Lauds, Vespers, Compline) which conclude with a canticle from the Gospel (Magnificat, Benedictus, Nunc dimittis); otherwise it is sung at the beginning of the Hour.
The Bugnini breviary has now “made order” in that it placed the hymn at the beginning of each Hour. He who has never experienced the ancient system, and in particular he who does not take the sung choral Office as his basic experience or norm, may easily claim that it is only a minor difference, not worthy of mention. But anyone who has had sufficient opportunity to experience Lauds or Vespers in actual liturgical celebration will know how immensely the traditional structure contributed to the effectiveness of the Hour, which was guided by liturgical sensitivity to the exigencies of real life, and not by a mechanical system. This order, which was animated by the spirit of prayer and can only be understood and judged in its life-functions, came into existence through the concatenation of logical, theological, psychological and artistic forces.
Laszlo Dobszay, The Bugnini-Liturgy and the Reform of the Reform (2003)