 Several octaves overlapped, so that, for instance, on 29 December the prayer of the saint of the day, Saint Thomas Becket, was followed by the prayers of Christmas Day, of Saint Stephen, of Saint John the Evangelist and of the Holy Innocents.The situation remained such until the reform of Pope Pius X.To cut down on the monotony of repeating the same prayers in Mass and Office every day for eight days, Pope Pius X classified the octaves as "privileged", "common" or "simple"

The privileged octaves were of three "ranks".