The introduction to Holy Week in my 1962 Roman Missal (Suumorum Pontificum edition, published 2012 by Baronius Press) gives a splendid account and justification for the sweeping reforms to the celebration of the Holy Week rites, authorised by Pope Pius XII from 1951 onwards.

“Originally those (Holy Week rites) were performed at the hour of day at which had occurred the scenes liturgically represented. Thus Mass on the Thursday was celebrated, as the Last Supper had been, in the evening; the liturgical action on the Friday took place, as had taken place the climax of Our Lord’s Passion, in the afternoon; and late on the Saturday evening began the solemn vigil that ended early the first day of the week with the Resurrection.

“In the Middle Ages various causes conspired to bring them forward earlier and earlier into the day, so that eventually they became morning functions, impairing the earlier harmony with the accounts given in the Gospel narratives. This disharmony was most glaring on the Saturday, which became liturgically the day of the Resurrection instead of that day’s eve, and, liturgically again, mourning became a day of light and gladness.

In 1642 the Sacred Triduum was removed from the days of obligation… the beautiful solemn liturgy of Holy Week had by this time become unknown to and unappreciated by all save the clergy and a handful of the faithful. A partial remedy was sought by introducing extra-liturgical devotions each evening (Holy Hour, Three Hours, Mater Dolorosa sermon, Stations of the Cross); but these lack much of the great dignity and sacramental power and efficacy of liturgical celebrations.

“To bring an end to this serious loss liturgists, parish clergy and Bishops in every part of the world have for long begged the Holy See to restore the liturgical actions of the Sacred Triduum to their proper hours in the evening. This was a serious undertaking, calling for much thought and consultation.

“In 1951 the Easter Vigil liturgy was restored to late evening by way of experiment, and in 1953 the Apostolic Constitution Christus Dominus permitted Mass to be said and Communion to be received on certain days in the year. From every country to Holy See received reports of greatly increased attendance and fervour. A Commission was appointed to investigate further and propose definite action, and the Sacred Congregation of Rites concurred with the action proposed. The Restored Ordo for Holy Week was published in November 1955. …

Not only have the times been radically altered, but the ceremonies themselves have been modified. This is mainly by way of shortening and simplification: and the intention is to make the main ideas of each function stand out more clearly. For the most part these changes are not innovations. They are mainly a return to an older form, more in line with what was known in the days of St Wilfrid and St Bede.

The desire of the Holy See in all this is that the Holy Week Liturgy should be celebrated everywhere with the greatest solemnity possible, and that the people should in some way take an active share. ” (pp 477 – 479)