Question: Is the Kyrie in Greek or Latin? Are there any other non-Latin words in the Mass? Why are the chants for the Kyrie so much more elaborate than any of the other parts of the Mass?
Answer: Until sometime in the third century, the Roman Mass was celebrated in Greek, the international language of the ancient world -- but historians don't believe that is the reason for the Greek Kyrie. Most are agreed that we have the Kyrie as the result of borrowing from an Eastern Rite, during the time when Latin had already displaced Greek. In the Byzantine Liturgy there are litanies in which the deacon or priest asks God for the various things needed by those of the Church Militant. Each petition is answered by the people "Kyrie eleison -- Lord have mercy." The following is a portion of the opening litany, at about the same position in the Mass as our Kyrie:
No less an authority than Pope Saint Gregory the Great describes the litany as it had been incorporated into the Roman Mass of His time (590-604):
Later, when the litany had fallen into disuse, and when Mass was sung, there was an even greater opportunity to "dwell on these prayers" by embelishing the music in the manner familiar to us today. In some cases the music became complicated beyond the ability of the average person to sing, and the Kyrie was turned over in whole or in part to a trained "schola" of singers.
Around the ninth century, composers began to add words to the complex melodies in order to make the number of syllables more closely agree with the number of musical notes. Such "farcing" or "troping" of the original texts produced a large number of texts. Arrangements varied -- in some works the farcing would preceed the invocations; in others it might follow; and in still others it might separate the two words of each invocation, making them the first and last word of eached troped sentence
The reader may notice that the beginning of this trope, "Lux et origo," is the name given to Mass #1, which is prescribed for paschaltide. In like manner, many of the other Masses in the Roman Gradual take their names from the tropes which were formerly associated with their Kyrie. A few such Masses (the plainer ones) do not have names -- probably because their Kyries do not have many extra notes to farce.
Mass #6, Kyrie Rex Genitor, appears to be a Sarum rite (English) composition, which illustrates the style of separating the words of the invocations:
rex genitor ingenite, vera essentia, eleison.
Kyrie, luminis fons rerumque conditor, eleison.
Kyrie, qui nos tuæ imaginis signasti specie, eleison.
Christi, Dei forma humana particeps, eleison....4
The mixture of Latin and Greek seems not to have bothered anyone, and some tropes were even more macaronic. The possibility of adding extra words to the Kyrie (and to other sung prayers), of course, gave rise to even more elaborate compositions, some beyond a reasonable length for most congregations. Pope Saint Pius V removed all of the farced pieces from his revised Roman Missal, but they are sometimes heard in the Mass compositions of the Renaissance and later, which are often performed in concert halls as works of musical art rather than in churches as worship.
The instruction of Pope Saint Gregory -- that we say "only Kyrie eleison and Christi eleison, so that the voices may dwell on these prayers (deprecationes) a little longer," ought to prompt us to pronounce the words slowly and clearly, avoiding the temptation to run their sylables together to save a few seconds.
In addition to the Kyrie, the Roman Mass mixes Latin with the Greek Trisagion on Good Friday:
. O Holy God.
Agios Ischyros. Sanctus Fortis. O Holy Strong One.
Agios Anthanatos. Sanctus Immortalis. O Holy Immortal
Eleison imas. Miserere nobis. Have mercy on us!
There are also a few words borrowed from Hebrew, such as "Amen," "Hosanna," and "Alleluia."