There is no proof of the existence of a definite system of notation before the seventh century. The chanters, priests, deacons, and monks, in applying melodies to the text of the office, composed by aid of their memories, and their melodies were transmitted by memory, although probably with the help of arbitrary mnemonic signs. The possibility of this will readily be granted when we consider that special orders of monks made it their sole business to preserve, sing, and teach these melodies. In the confusion and misery following the downfall of the kingdom of the Goths in the middle of the sixth century the Church became a sanctuary of refuge from the evils of the time. With the revival of religious zeal and the accession of strength the Church flourished, basilicas and convents were multiplied, solemnities increased in number and splendor, and with other liturgic elements the chant expanded. A number of popes in the seventh century were enthusiastic lovers of Church music, and gave it the full benefit of their authority. Among these were Gregory II. and Gregory III., one of whom may have inadvertently given his name to the chant. The system of tonality upon which the music of the Middle Age was based was the modal or diatonic. The modern system of transposing scales, each major or minor scale containing the same succession of steps and half steps as each of its fellows, dates no further back than the first half of the seventeenth century. The mediaeval system comprises theoretically fourteen, in actual use twelve, distinct modes or keys, known as the ecclesiastical modes or Gregorian modes. These modes are divided into two classes—the “authentic” and “plagal.” The compass of each of the authentic modes lies between the keynote, called the “final,” and the octave above, and includes the notes represented by the white keys of the pianoforte, excluding sharps and flats. The first authentic mode begins on D, the second on E, and so on. Every authentic mode is connected with a mode known as its plagal, which consists of the last four notes of the authentic mode transposed an octave below, and followed by the first five notes of the authentic, the “final” being the same in the two modes. The modes are sometimes transposed a fifth lower or a fourth higher by means of flatting the B. During the epoch of the foundation of the liturgic chant only the first eight modes (four authentic and four plagal) were in use. The first four authentic modes were popularly attributed to St. Ambrose, bishop of Milan in the fourth century, and the first four plagal to St. Gregory, but there is no historic basis for this tradition. The last two modes are a later addition to the system. The Greek names are those by which the modes are popularly known, and indicate a hypothetical connection with the ancient Greek scale system. Authentic Modes Plagal Modes