In the singing of the mediaeval hymn melodies, many beautiful examples of which abound in the Catholic office books, the above rules of rhythm and expression are modified as befits the more regular metrical character which the melodies derive from the verse. They are not so rigid, however, as would be indicated by the bar lines of modern notation, and follow the same laws of rhythm that would obtain in spoken recitation. The liturgic chant of the Catholic Church has already been alluded to under its more popular title of “Gregorian.” Throughout the Middle Age and down to our own day nothing in history has been more generally received as beyond question than that the Catholic chant is entitled to this appellation from the work performed in its behalf by Pope Gregory I., called the Great. This eminent man, who reigned from 590 to 604, was the ablest of the succession of early pontiffs who formulated the line of policy which converted the barbarians of the North and West, brought about the spiritual and political autonomy of the Roman See, and confirmed its supremacy over all the churches of the West. In addition to these genuine services historians have generally concurred in ascribing to him a final shaping influence upon the liturgic chant, with which, however, he probably had very little to do. His supposed work in this department has been divided into the following four details: (1) He freed the church song from the fetters of Greek prosody. (2) He collected the chants previously existing, added others, provided them with a system of notation, and wrote them down in a book which was afterwards called the Antiphonary of St. Gregory, which he fastened to the altar of St. Peter’s Church, in order that it might serve as an authoritative standard in all cases of doubt in regard to the true form of chant. (3) He established a singing school in which he gave instruction. (4) He added four new scales to the four previously existing, thus completing the tonal system of the Church.