For some years longer Paris continued to be, as it had been for more than two hundred years, the musical centre of Europe. The prestige it had held so long was lost, ultimately, not only through an actual decline of original power, but through an abuse of the power they possessed. The standards of the old organ masters of Notre Dame, if somewhat dry, were at least scholarly; but we begin to see, in the early fourteenth century, a deterioration, and a tendency among singers to make a display of their ability in improvisation. Canons and rounds of that time, and even long after, were written in a kind of shorthand, understood, presumably, by every trained singer, but nevertheless giving some freedom of judgment to the performer, which was easily abused. The first phrase of the cantus firmus was usually written out; after this a few signs in Latin, meaning nothing to the modern musician unskilled in the mysteries of this art, would indicate the time of entrance and relative pitch for the other voices. Imitation was almost continuously in use; the 'accidentals’ of modern notation were but rarely indicated, even as late as the time of Palestrina, and the 'key signature’ of the present day was unknown. However, the training of the chapel singers was such as to give a thorough knowledge of the use of accidentals and of the musical symbols of the time. Intricate rules for their guidance were laid down; but, carried away by the flood of new ideas, and unrestrained by scholarly fastidiousness, many of them indulged in liberties which loaded down the pure melody of the venerable plain-chant with inappropriate ornamentations, and often rendered it hopelessly unrecognizable. In protest against these unwarranted melismas and tasteless innovations of singers, especially of the cathedral choirs and of the papal chapel, the famous bull of 1322 was issued by Pope John XXII. It was not a protest, primarily, either against the popular faux-bourdon, which was generally in use until after the return of the papacy to Rome (1377), or the contrapuntal school, _per se_. It was certainly not against the methods of the ars nova, as is proved by the use of certain technical terms peculiar to the _ars antiqua_. It is against the abuses of the latter school, the obscuring of the plain-song melodies and the violation of the spirit of church music by frivolous rhythmic variations, ornamentation, and juggling with counter melodies, often of profane character. Many other protests of a like nature came from the papal chair during the next two hundred and fifty years; and we shall have occasion to see, in a later chapter, the result of the struggle between religious decorum, on the one hand, and, on the other, the vagaries of the artistic mind in the throes of development.