Kyrie Eleison (Greek for "Lord have mercy"; the Latin transliteration supposes a pronunciation as in Modern Greek) is a very old, even pre-Christian, expression used constantly in all Christian liturgies. Arrian quotes it in the second century: "Invoking God we say Kyrie Eleison" (Diatribæ Epicteti, II, 7). A more obvious precedent for Christian use was the occurrence of the same formula in the Old Testament (Psalm 4:2, 6:3, 9:14, 25:11, 121:3; Isaiah 33:2; Tobit 8:10; etc., in the Septuagint). In these places it seems already to be a quasi-liturgical exclamation. So also in the New Testament the form occurs repeatedly (Matthew 9:27, 20:30, 15:22; Mark 10:47; Luke 16:24, 17:13). The only difference is that all these cases have an accusative after the verb: Kyrie eleison me, or eleison hemas. The liturgical formula is shortened from this.
It is not mentioned by the Apostolic Fathers or the Apologists. The first certain example of its use in the liturgy is in that of the eighth book of the "Apostolic Constitutions". Here it is the answer of the people to the various Synaptai (Litanies) chanted by the deacon (Brightman, "Eastern Liturgies", pp. 4 and 5; cf. "Ap. Const.", VIII, vi, 4). That is still its normal use in the Eastern rites. The deacon sings various clauses ofa litany, to each of which the people answer, Kyrie Eleison. Of the Greek Fathers of the fourth century, Eusebius, Athanasius, Basil, Cyril of Jerusalem, and the two Gregories [of Nazianzus and Nyssa] do not mention it. But it occurs often in St. John Chrysostom. Its introduction into the Roman Mass has been much discussed. It is certain that the liturgy at the Rome was at one time said in Greek (to the end of the second century apparently). It is tempting to look upon our Kyrie Eleison as a surviving fragment from that time. Such, however, does not seem to be the case. Rather the form was borrowed from the East and introduced into the Latin Mass later. The older Latin Fathers, Tertullian, Cyprian, etc., do not mention it. Etheria (Silvia) heard it sung at Jerusalem in the fourth century. It is evidently a strange form to her, and she translates it: "As the deacon says the names of various people (the Intercession) a number of boys stand and answer always, Kyrie Eleison, as we should say, Miserere Domine" (ed. Heræus, Heidelberg,1908, XXIV, 5, p. 29). The first evidence of its use in the West is in the third canon of the Second Council of Vaison (Vasio in the province of Arles), in 529. From this canon it appears that the form was recently introduced at Rome and in Italy (Milan?): "Since both in the Apostolic See as also in all the provinces of the East and in Italy a sweet and most pious custom has been introduced that Kyrie Eleison be said with great insistence and compunction, it seems good to us too that this holy custom be introduced at Matins and Mass and Vespers" (cf. Hefele-Leclercq, "Histoires des Conciles", Paris, 1908, pp. 1113-1114; Duchesne, "Origines", p. 183). The council says nothing of Africa or Spain, though it mentions Africa in other canons about liturgical practices (Can. v). It appears to mean that Kyrie Eleison should be sung by the people cum grandi affectu. E. Bishop (in the "Downside Review", 1889) notes that this council represents a Romanizing movement in Gaul.
The next famous witness to its use in the West is St. Gregory I (590-604). He writes to John of Syracuse to defend the Roman Church from imitating Constantinople by the use of this form, and is at pains to point out the difference between its use at Rome and in the East: "We neither said nor say Kyrie Eleison as it is said by the Greeks. Among the Greeks all say it together, with us it is said by the clerks and answered by the people, and we say Christe Eleison as many times, which is not the case with the Greeks. Moreover in daily Masses some things usually said are left out by us; we say on Kyrie Eleison and Christe Eleison, that we may dwell longer on these words of prayer" (Ep. ix in P.L., LXXVII, 956). The last words appear to mean that sometimes other prayers are left out that there may be more time for singing the Kyrie Eleison. We also see from this passage that in St. Gregory's time the special Roman use of the alternative form Christe Eleison (unknown in the Gallican and Eastern rites) existed. It seems inevitable to connect the Kyrie Eleison in the Roman Mass with an original litany. Its place corresponds exactly to where it occurs as part of a litany in the Syrian-Byzantine Liturgy; it is still always sung at the beginning of litanies in the Roman Rite too, and St. Gregory refers to "some things usually said" in connection with it. What can these things be but clauses of a litany, sung, as in the East, by a deacon? Moreover there are still certain cases in the Roman Rite, obviously of an archaic nature, where a litany occurs at the place of the Kyrie. Thus the last clause (Kyrie Eleison, repeated three times; Christe Eleison, repeated three times; Kyrie Eleison, repeated three times) is sung as the celebrant says the first prayers of the Mass, and correspond in every way to our usual Kyrie. So also at ordinations the Litany is sung towards the beginning of the Mass. In this connection it may be noted that down to the late Middle Ages the Kyrie of the Mass was left out when it had just been sung in a Litany before Mass, as on Rogation days (e.g., Ordo Rom., XI, lxii). We may suppose, then, that at one time the Roman Mass began (after the Introit) with a litany of general petitions very much of the nature of the third part of our Litany of the Saints. This would correspond exactly to our great Synapte in the Syrian Rite. Only, from what has been said, we conclude that the answer of the people was in Latin — the "Miserere Domine" of Etheria, or "te rogamus, audi nos", or some such form. About the fifth century the Greek Kyrie Eleison was adopted by the West, and at Rome with the alternative form Christe Eleison. This was then sung, not as in the East only by the people, but alternately by cantors and people. It displaced the older Latin exclamations at this place and eventually remained alone as the only remnant of the old litany.
The first Roman Ordo (sixth-seventh cent.) describes a not yet fixed number of Kyries sung at what is still their place in the Mass: "The school [schola, choir] having finished the Antiphon [the Introit] begins Kyrie Eleison. But the leader of the school watches the Pontiff that he should give him a sign if he wants to change the number of the litany" ("Ordo Rom. primus", ed. Atchley, London, 1905, p. 130). In the "Ordo of Saint Amand", written in the eighth century and published by Duchesne in his "Origines du culte" (p. 442), we have already our number of invocations: "When the school has finished the Antiphon the Pontiff makes a sign that Kyrie Eleison should be said. And the school says it [dicit always covers singing in liturgical Latin; cf. the rubrics of the present Missal: "dicit cantando vel legendo" before the Pater Noster], and the Regionarii who stand below the ambo repeat it. When they have repeated it the third time the Pontiff signs again that Christæ [sic] Eleison be said. This having been said the third time he signs again that Kyrie Eleison be said. And when they have completed it nine times he signs that they should stop." So we have, at least from the eighth century, our present practice of singing immediately after the Introit three times Kyrie Eleison, three times Christe Eleison, three times Kyrie Eleison, making nine invocations altogether. Obviously the first group is addressed to God the Father, the second to God the Son, the third to God the Holy Ghost. The medieval commentators are fond of connecting the nine-fold invocation with the nine choirs of angels (Durandus, "Rationale", IV, xii). From a very early time the solemnity of the Kyrie was marked by a long and ornate chant. In the Eastern rites, too, it is always sung to long neums. It is still the most elaborate of all our plainsong melodies. In the Middle Ages the Kyrie was constantly farced with other words to fill up the long neums. The names of the various Kyries in the Vatican Gradual (for instance, Kyrie Cunctipotens genitor Deus of the tenth century, Kyrie magnæ Deus potentiæ of the thirteenth century, etc.) are still traces of this. As an example of these innumerable and often very long farcings, this comparatively short one from the Sarum Missal may serve:
Kyrie, rex genitor ingenite, vera essentia, eleyson.
Kyrie, luminis fons rerumque conditor, eleyson.
Kyrie, qui nos tuæ imaginis signasti specie, eleyson.
Christe, Dei forma humana particeps, eleyson.
Christe, lux oriens per quem sunt omnia, eleyson.
Christe, qui perfecta es sapientia, eleyson.
Kyrie, spiritus vivifice, vitæ vis, eleyson.
Kyrie, utriqusque vapor in quo cuncta, eleyson.
Kyrie, expurgator scelerum et largitor gratitæ quæsumus propter nostrasoffensas noli nos relinquere, O consolator dolentis animæ, eleyson (ed. Burntisland, 929).
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