It has already been related how, even as early as 1322, the liberties which careless, ignorant, or sacrilegious singers took with the Roman service had called forth denunciations from the papal chair. The genius of the Netherland schools, dominating church music as it did for a space of two hundred years, was, like Janus, two-faced. On the one hand, it developed a musical technique so complete and perfect in form that any further progress without an entire change of principle seemed impossible; and, on the other, it fostered a dry, mathematical correctness that led, at its worst, to an utter disregard of expression and feeling. Only the genius of a Josquin or a Lasso rendered learning subservient to beauty of expression and carried out the true mission of art. In Rome, however, no master had yet appeared who was great enough to force into the background all the unsanctioned innovations by which unscrupulous musicians sought to reach the popular taste. From the time of the return of the popes from Avignon (1377) Roman church music had been a continual source of dissatisfaction to the Curia. As has been pointed out, the plain-chant became more and more overladen with contrapuntal embellishments; the mass sometimes exhibited a labored canon worked over a long, slow _cantus firmus_, the different voices singing different sets of words entirely unconnected with each other. Sometimes, again, the ritual was enlivened by texts beginning with the words _Baisez moy; Adieu, mes amours_; or the much tortured _Omme armé_, of which the tunes were as worldly as the text. If these objections were lacking, another was likely to be present in the absurdly elaborate style, which rendered the words of so little importance that they might as well not have existed at all. The mass, 'bristling with inept and distracting artifices,’ had lost all relation to the service it was supposed to illustrate. 'It was usual for the most solemn phrases of the Kyrie, Gloria, Credo, or Agnus Dei to blend along the aisles of the basilica with the unedifying refrains of the lewd chansons of Flanders and Provence.’[123] In this manner the beautiful ritual was either degraded by pedants into a mere learned conundrum, or by idlers into a sacrilegious and profane exercise; and the reproofs of popes and councils had, so far, not availed to keep out these signs of deterioration, much less to lift church music to the level of the sister arts.