After the death of Saint Ambrose the original purity of plain chant melodies was corrupted. When in 590 Gregory I. became Pope. church music was in a deplorable state. Recognizing the fact that music is one of the greatest aids to religion. Gregory began his reforms by establish ing the Nchola Cantorum, which in a very short time rose to an institution of the highest impor tance and for centuries preserved the ancient tra ditions. Since the time of Saint Ambrose a large number of new hymns had been composed. The old monotony of the chants had given place to a more varied melody, and this naturally led to an extension of the compass beyond the original fifth. The four original or authentic modes were no longer sufficient. Gregory is credited with having established the four plagal Modes to meet the de mands of the advanced art. Besides, be also se lected the chants that were to be sung on every day throughout the Church year. The texts and melodies he ordered to he written in a book called which was de clared to be the absolute authority in mat tars of church music. The system of notation employed in this book is that known as Neumes (q.v.). consisting of various signs placed above the syllables without employment of a staff. After plain chant had thus been re formed it spread with astonishing rapidity over all Europe. Especially Charlemagne was instru mental in promulgating this Cantus Roman us; for at diets held at Aix-la-Chapelle in S03 and Diedenhofen in 805 he issued strict orders to in troduce this manner of singing in all the dioceses of his empire, and established singing-schools in various cities, as Soissons. Toil, Orleans. Cam bray, Lyons, and Dijon. Even before the acces sion of Charlemagne singing-schools had been founded at Fulda and Saint Gall. but as new hymns were constantly being written, the purity of the style was almost certain to suffer. Thus in 1323 Pope John XXII. was obliged to issue a bull restraining musicians from unlawful innova tions. Acting upon the recommendation of the Council of Trent, Pope Gregory XIII. in 1576 took active steps towards a purifi cation of the style of church music. But by that time the art of music had made enormous strides: polyphonic music had arisen. Although the new music had never been officially sanctioned, it was not only tolerated, but was favored. Composers were in the habit. of taking the old plain chant melodies as a maims firmus for the tenor, against which the other voices were set contrapuntally. Many composers had little scruple in distorting the original melodies to suit their purpose. But a greater danger to church music arose from the fact that it became customary to substitute popu lar secular melodies for the plain chant. At this time Palestrina established the true polyphonic church style. This is founded upon the church modes; simplicity and noble dignity are its fun damental principles, as they ever have been the principles of plain chant. Since the time of Palestrina no new melodies have been added to the large stock of plain chant. Composers have de voted their talents to polyphonic music, but the old plain chant melodies have remained in con stant use up to the present day. The custom at High Mass is to sing the Kyrie, Gloria, Credo, sanetus, and 3gnus Dei in polyphonic or modern harmonic style with instrumental accompaniment.
The Introit, Gradual, Tract (or Sequence), Offer tory. and Communion, if sung by the choir. are sung in unison to the old plain chant melodies, to which the organ supplies the harmonies strict ly in accordance with the rules governing the church modes. The corda, Preface, and Pater nosier are set to the ancient unvarying melodies. The advance of musical archicology during the past century has done much toward the restoration of the plain chant melodies to their original purity. Pope Pius IX. ordered the Sacred Congregation of Rites to revise and pub lish, with the sanction of the Holy See, the en tire treasure of plain chant melodies. The first volume appeared in Ratisbon in 1871, and within ten years the work of revision was completed.
The discovery and study of old manuscripts during the last half of the nineteenth century has brought to light many facts formerly not known. Some scholars cast doubt upon the work common ly ascribed to Gregory I. But the old tradition was not seriously shaken until the learned F. A. Gevaert in 1800 published his book, Les origines du chant lituryique de reglise latine, in which he attacks with weighty arguments the position ascribed to Gregory in the development of plain chant. But this was only the precursor of an other book, Lit metope(' antique dans le chant de Peglise latine. which appeared in 1895. The first work had raised a host of opponents who were un willing to surrender a thousand-year-old tradi tion. In the second book, a work of stupendous learning, Gevaert meets all objections with proofs drawn from various ancient manuscripts and even strengthens his original statements. The impor tant points brought out by the investigation of Gevaert are as follows: (1) The claims made by the adherents of tradition in favor of Gregory cannot he established on any historical grounds. (2) It is' a legend that originated during the reign of Charlemag,ne or slightly earlier. (3) It was not generally accepted until the eleventh century. (41 The work of the compilation and composition of the chants of the Liturgy was in reality the work of the Greek popes that occupied the Papal chair at the end of the seventh and the beginning of the eighth century. (5) The melo dies of the Antiphouale Missaram received their final form between the acces.ion of Leo II. ((S2) and that of Gregory II. (715). The Pope that was particularly active in this work was Sergius I. (687-7011. (6) The Antiphonale Oilicii had received its final shape during the pontificate of Agatha (678-6S1). Each of these points Gevaert establishes on the strength of ancient documents of unquestioned authenticity.
For a technical exposition of the nature and history of plain chant, consult Cevaert's learned work already cited. 1.a antique dans le chant de realise latine (Client. 1S 95) . Other works are: Haberl, Nagister Choralis (Rat isbon. 1896) ; P. Wagner. Einf tihrutay in die yr, yorianischen Ilehaln n (I'reiburg, .1895); Ilriggs, History and CharaehrINties of Swig ( London, 1891) ; Looters, La theorie musicale flu chant n (Park. 1895) Bonuzzi. ludo tforetiro•practitn di canto gregoriano ti9I Pot hi T, LI'S u,0w1Xs ncs ('rournay, 1880) ; Dickinson, .1/lisle in the History of the Th(sttrit Church (New York,