GREGORIAN CHANT OR TONES, the name given to certain choral melodies intro duced into the service of the early Christian church by pope Gregory the great, who flourished towards the end of the 6th century. The music of the church in earlier times was founded on the Greek system, as far as it could be used, which was improved from time to time, until St. Ambrose, bishop of Milan, in the 4th c. invented the Ambrosian chant. See AMBROSTAN CHANT. In 599 pope Gregory began to reform and improve the music of the church at Rome, by discarding the Greek tetrachord, or scale, on the basis of a fourth, and in its place substituting the scale of the octave, which some writers say he named by the letters of the alphabet, while others say he had a pecular set of. signs called notes Romana, consisting partly of words with points, strokes, and other marks, which sufficiently served his purpose. To the authentic modes of Ambrosius, Gregory added the plagal, which began with the fourth below, and thus lie completed the octave. He retained the four most useful modes of the Ambrosian chant, termed the _Dorian, Phrygian, Lydian, and Mixolydian, which are supposed to have been obtained from the ancient Greeks. At first Gregory's improvement was called the Roman chant, but later it got the name of eanturn planum or firmum, as it was originally sung in unison, and in notes all of the same length. At a later period the letters of the Roman, as well as of the Greek alphabet, were used to express the notes of the Gregorian chant, 'blot without any general fixed order or rule. In the course of time, the system of nota tion on lines and spaces came into use; but at first only four lines were used, on which we find all the old examples of the Gregorian chant written. By the Gregorian tones, or modes (toni, modz) of Gregory, must be understood in certain melodious formula, made out of the union of a perfect fifth and a perfect fourth, or their inversion, to give time church-song greater variety. All the old writers agree as to the diatonic genus of the Gregorian tones, but they do not all agree as to the number of the tones; sonic count ing fourteen, others twelve, while in some old Roman choral-books we find only eleven.
The foundation of the system of the Gregorian tones may be explained thus: As there are seven notes from a to g, there should be at least seven different modes, or tone systems, varying from each other according to the position of the semitones; but as the final or key-note of each mode might be the first note, or might be in the middle, the same scale could therefore, as it were, be viewed from two sides, which gave rise to the fourteen system of tones. It was, however, found that two of those were at variance with a fundamental rule of church-song—viz., that every mode or scale must possess a perfect fifth or perfect fourth; and that the modes containing a false fifth from 1) natural to f natural, or a false fourth from f to b, could not be used, and on account of the dis sonant character of these intervals must be rejected. This reduced the number of tones to twelve. It was further found, that as four of the twelve were merely transpositions of some of the others, there were really only eight, and that they were in every respect sufficient for all the purposes of church-song. The eight Gregorian,tones, as they are handed down toAiS, Were in time fixed by a 'royal mandate of Charles the great—octo tont suftere videntur. The following example in modern notation in the G clef will show the position of the eight Gregorian tones: There cannot be little doubt that pope Gregory greatly improved the church-music at the time, and that the eight tones have always been ascribed to him. That they are of great antiquity is certain, for we find them mentioned in a treatise on choral singing by one Aurelian in the 9th century. The different character of the Gregorian tones depends entirely on the places of the semitones, which in the above example are marked with Several of the tones have various endings, some as many as four, while the sec ond, fifth, and sixth tones have each only one ending. For a full and interesting account of the Gregorian church-music, see N. A. Janssen's Grundregeln des Gregorianschen Kirchengesanges, published by Schott in Mainz, 1846.