In like manner in the Middle Ages poetry and music strove for supremacy. After the solemn melodies of St. Gregory, linked so closely with the words, had comforted, inspired and sustained the Western World in a time of her deepest abasement, song, which had been hitherto for one voice, developed into polyphony, and with this mighty advance in music the friendly relations between these arts was once more disturbed. In the joy at overcoming difficulties which part-music offered the composers as well as the singers, the former completely lost sight of their duty toward the words, and were so utterly indifferent to the text of vocal work that they did not hesitate to use in the same piece two poems upon quite different subjects, yes, even in different languages, and in so doing argued, and not without reason, that in the intricacy of the vocal parts the words would scarcely be heard. At the appearance of the modern opera in the year 1600, the struggle of the two sister-arts was especially severe. Even as proposed by its founders, who saw in it a revival of the antique drama, poets and composers, during the first decades, were eager to coöperate. When, however, the passion for the opera was no longer confined to the circle of the aristocracy, when special buildings had been erected to which the public could gain access for a consideration (the "Cassiano" in Venice, in 1637, being the first), the noble simplicity striven for by those lovers of antiquity came to an end. The popular craving for the spectacular and the desire for music which was pleasing to the ear strongly affected the further growth of the opera. In Italy, which country in the course of the seventeenth and eighteenth centuries set the fashion for all Europe in operatic and musical matters, the public was especially enthusiastic over strong, well-trained voices. No matter how high the point of perfection reached by the art of singing, the singers, male and female, received but one-sided recognition. Soon these obtained undisputed control of the opera; in order to please the taste of the masses, directors, even poets and composers felt obliged to surrender. For them only was the libretto arranged, and in order to satisfy their vanity did the composer tax his imagination. In vain did truly artistic men--among them the Venetian composer Benedetto Marcello with his satire "Il teatro alla moda" (1720)--raise their voices against "the mighty abuse of music at the cost of the sister-arts," their warning words fell unheeded. It was reserved for a German, after a desperate struggle, to put an end to the nuisance of the singers' sovereignty and to give once more to the opera a truly artistic significance, and this German was Gluck.