The success of Monteverde had its natural result. He soon had pupils and imitators by the score. The Venetians speedily discovered that they had an inherent taste for opera, and the musicians of the day delighted to cater for it. Monteverde's most famous pupil was Cavalli, to whom may with some certainty be attributed an innovation which was destined to affect the future of opera very deeply. In his time, to quote Mr. Latham's 'Renaissance of Music,' 'the _musica parlante_ of the earliest days of opera was broken up into recitative, which was less eloquent, and aria, which was more ornamental. The first appearance of this change is to be found in Cavalli's operas, in which certain rhythmical movements called "arias" which are quite distinct from the _musica parlante_, make their appearance. The music assigned by Monteverde to Orpheus when he is leading Eurydice back from the Shades is undoubtedly an air, but the situation is one to which an air is appropriate, and _musica parlante_ would be inappropriate. If the drama had been a play to be spoken and not sung, there would not have been any incongruity in allotting a song to Orpheus, to enable Eurydice to trace him through the dark abodes of Hades. But the arias of Cavalli are not confined to such special situations, and recur frequently,' Cavalli had the true Venetian love of colour. In his hands the orchestra began to assume a new importance. His attempts to give musical expression to the sights and sounds of nature--the murmur of the sea, the rippling of the brook and the tempestuous fury of the winds--mark an interesting step in the history of orchestral development. With Marcantonio Cesti appears another innovation of scarcely less importance to the history of opera than the invention of the aria itself--the _da capo_ or the repetition of the first part of the aria in its entirety after the conclusion of the second part. However much the _da capo_ may have contributed to the settlement of form in composition, it must be admitted that it struck at the root of all real dramatic effect, and in process of time degraded opera to the level of a concert. Cesti was a pupil of Carissimi, who is famous chiefly for his sacred works, and from him he learnt to prefer mere musical beauty to dramatic truth. Those of his operas which remain to us show a far greater command of orchestral and vocal resource than Monteverde or Cavalli could boast, but so far as real expression and sincerity are concerned, they are inferior to the less cultured efforts of the earlier musicians. It would be idle to attempt an enumeration of the Venetian composers of the seventeenth century and their works. Some idea of the musical activity which prevailed may be gathered from the fact that while the first public theatre was opened in 1637, before the close of the century there were no less than eleven theatres in the city devoted to the performance of opera alone.