of Aristoxenus, falsely attributed to Ptolemy. The editing of that part of the _Liber Antiphonarius_ which has become our Gradual was probably due to the Syrian pope, Gregory III, who was very active in the promotion of liturgical music. The _Antiphonarium Romanum_, or complete collection of liturgical chants of the church--consisting of several hundred pieces--is divided into two distinct parts--the _Antiphonarium_ proper and the _Gradual_. The former contains the offices of the canonical hours (_cursus ecclesiasticus_), consisting of the responses, anthems, and hymns reiterated day and night by religious communities. The custom of reciting the office began among the monastic orders of the Orient about the fourth century. Apparently it had its genesis in Antioch, about 350, and soon spread to the other Greek churches. The pilgrim in Silvia speaks of hearing the Vigils and other hours in the church of Jerusalem (386), and Bishop Cassian of Autun found the hour of Prime introduced at Bethlehem in 390. From Alexandria and Constantinople the office passed to Milan and Rome. In the sixth century it was organized somewhat as it is to-day. Cassiodorus (_ca._ 540) names seven _synaxes_, or daily reunions, and a similar number is mentioned in the rules of St. Benedict about the same time. The _Gradual_ consists of the services of the mass, and contains the anthems, responses, and hymns proper to these services. There are a few fixed pieces, such as the _Kyrie_, _Gloria_, _Sanctus_, _Agnus Dei_, and _Credo_, constituting what is known as the Ordinary of the mass, and besides these there are a large number which vary according to the day and the name of the saint whose feast is celebrated. The chants belonging to the Introit and Communion are antiphonal, while those of the Gradual, Alleluja, Tractus, and Offertory are responsorial. The _Gloria in excelsis_ is a sort of hymn. Besides the hymns of the Ambrosian cycle, already spoken of, the Latin church adopted many Oriental hymns of the seventh and eighth centuries. Fourteen hymns of great age are still included in the Gradual, among them the _Pange lingua_, attributed to Fortunatus, the _Vexilla regis_, and the _Veni creator spiritus_, attributed to Charlemagne. The hymns, anthems, and responses in the general repertory of church songs appear under two distinct forms--simple melodies and ornate melodies. The former, which are more or less syllabic, are used for all the anthems in the _cursus ecclesiasticus_ and the responses belonging to that part of it which forms the office of the day. The ornate style is used for the anthems and responses of the mass and for the office of the night. The responses of the Gradual, Tractus, and Alleluja are musically the most interesting of the liturgical chants. They are not so much an integral part of the sacrifice of the mass as they are a sort of vocal intermezzo for solo and chorus, allowing the display of considerable art, both in technique and expression.