=Contribution of the Paris School=.—When the Paris school ceased to be of utmost importance to the world of music it had bequeathed to the later schools Measured Music, and its forms of Organum, Motet, Conductus and Roundel, and the use of certain not unpleasing intervals, though occasional consecutive fourths, fifths, and octaves appeared. It was, then, the business of the Gallo-Belgic school to refine these intervals, develop measured music, and so improve and develop these old primary forms, eliminating some and evolving others, as to give the school of the Netherlands, one century later, forms pleasing in intervals and of sufficient unity and design to afford opportunity for the infusion of the emotional. In the matter of intervals much was done to develop and use the old ones, excepting the consecutive fourths and fifths which were abolished never to appear again, and many new, or previously unused intervals, were made use of. In the matter of forms, we hear no more of the crude Organum and Conductus, but a little about the Motet, and nothing at all in regard to the Roundel, as such. It is, however, due entirely to this last form that polyphonic music developed; though we hear no more of the Roundel, we do hear much in regard to the Canon, and the Canon was but a highly developed species of the Roundel. =Imitation and the Canon=.—The use of Imitation, as we have seen, gradually became more and more important. The old monks, in the very beginning, imitated melody in the fourth and fifth; at the time of the Paris school these melodies were combined with new ones making Imitation with more than one melody, though the melody underwent no real organic development. Now we see in the inception of the Canon a development of real Imitation of only one melody, but given _Variety_ by use of the devices of Inversion, Augmentation, Diminution, etc. And not only did this occur in the Canon, but we find it also in the other forms, in a freer style, adding materially to the _Unity_. Imitation is the foundation principle of polyphonic music, and this principle was present in the crude efforts of the old monks, in the more intelligent efforts of the Paris school, and now for the first time, receives, in the Gallo-Belgic school, a partial recognition of its real value, and a commensurate use. [Music] Naumann, History of Music, Vol. I, page 315, extract from a chanson by Dufay. Figure 1 shows the principal melody, figure 2 shows the same at the fifth below. The entire chanson is quoted in Naumann with the various imitations fairly well marked; the student should refer to it.