Annibale Bugnini, the architect of the Ordinary Form, in his work The Reform of the Liturgy : 1948–1975, (The Liturgical Press, 1990), Chap. 46.II.1, p. 773, explains why it was removed: "They got rid of texts that smacked of a negative spirituality inherited from the Middle Ages. Thus they removed such familiar and even beloved texts as the Libera me, Domine, the Dies Irae, and others that overemphasized judgment, fear, and despair. These they replaced with texts urging Christian hope and arguably giving more effective expression to faith in the resurrection".
This first video is of the Requiem Mass celebrated by the Institute of Christ the King, Sovereign Priest, on EWTN recently. Their superb schola cantorum renders the Dies Irae during the Mass. The Institute of Christ the King, Sovereign Priest, has recently received the approval of its statutes by the Holy See and has been given the status of 'Pontifical Right' under the Pontifical Commission Ecclesia Dei.
The text of the Dies Irae seems to be derived from the first Chapter of the Book of the Prophet Sophonias (Zephaniah, if you're reading a non-Catholic Bible) and is usually attributed to Thomas of Celano, who was a Franciscan during the lifetime of St. Francis of Assisi. Thomas of Celano is also attributed with the Vita Prima or first biography of St. Francis.
Like so many texts of the Traditional Latin Liturgy, it has inspired the finest composers for two millennia to create some of their most sublime masterpieces. The most obvious example is that of Mozart in his Requiem Mass, the first movement of which can be found in the second video. If this setting can just be considered more liturgical than operatic, it is in contrast with the later and more obviously operatic settings of, for example, Verdi in the third video.
Although we can clearly see that later settings often seek more for emotional effect than to inspire devotion and repentence among the living and prayer for the dead, it is certainly true that the texts of the Traditional Latin Liturgy stand for something that answers deeply to the yearning of the human heart. The following words are from the plea addressed to Pope Paul VI at the time when he proposed to reform the Liturgy and to consign, as it then seemed, to the rubbish heap of history, so much of our Catholic Heritage:
"...The rite in question, in its magnificent Latin text, has also inspired a host of priceless achievements in the arts - not only mystical works, but works by poets, philosophers, musicians, architects, painters and sculptors in all countries and epochs. Thus, it belongs to universal culture as well as to churchmen and formal Christians. In the materialistic and technocratic civilisation that is increasingly threatening the life of mind and spirit in its original creative expression - the word - it seems particularly inhuman to deprive man of word-forms in one of their most grandiose manifestations. The signatories of this appeal, which is entirely ecumenical and non-political, have been drawn from every branch of modern culture in Europe and elsewhere. They wish to call to the attention of the Holy See, the appalling responsibility it would incur in the history of the human spirit were it to refuse to allow the Traditional Mass to survive, even though this survival took place side by side with other liturgical reforms."
Source: Latin Mass Society of England and Wales website.
Mother of Sorrows, pray for the Holy Souls in Purgatory!