[T]his clause was apparently added in order that ARII [2009] stays valid under OCO2015.
But what you should do is consult OCO.parishes and religious houses which received the new Breviary in 1971 were faced with the impossible task of chanting an office which was not compiled with musical forms in mind.
Volume one completes a trio of texts which began with the publication of the Liber Hymnarius in 1983 and Antiphonale Romanum II in 2009. These three books provide the Gregorian notation for the antiphons, hymns, and responsories which are necessary to chant Lauds and Vespers from the modern Liturgy of the Hours on Sundays, feasts, and solemnities.
Unexpectedly, the Congregation for Divine Worship published a second edition of the Ordo Cantius Officii in 2015, which revised several of the antiphon selections of its predecessor. The need for this text arose in 2002 after Pope John Paul II introduced the three-year cycle of antiphons at the Gospel canticle.
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