However, the changes encompassed all aspects of sacred liturgy.
Indeed in 1961, a year ahead of Saint John XXIII's edition of the Missal becoming the Editio Iuxta Typicam and before the wholesale changes resulting in the Mass of Paul VI, the Roman Breviary or Breviarium Romanum was subject considerable reform and eventually even this final pre-council but none the less already reformed edition of the Divine Office gave way to the Liturgy of the Hours approved by Paul VI in the Apostolic Constitution The Canticle of Praise or Laudis Canticum in November 1970.
Over at Rotate Cæli, there is an interesting article which gives some insight into the transitional changes applied to the Breviary and particularly the Psalter. Click here to view what is a very interesting post.