While Gluck was altering the course of musical history in Vienna, another revolution, less grand in scope and more gradually accomplished, but scarcely less important in its results, was being effected in Italy. This was the development of opera buffa, a form of art which was destined, in Italy at any rate, to become a serious rival to the older institution of opera seria, and, in the hands of Mozart, to produce masterpieces such as the world had certainly not known before his day, nor is ever likely to see surpassed. There is some uncertainty about the actual origin of opera buffa. A musical comedy by Vergilio Mazzocchi and Mario Marazzoli, entitled 'Chi sofre speri,' was produced in Florence under the patronage of Cardinal Barberini as early as 1639. The poet Milton was present at this performance, and refers to it in one of his _Epistolae Familiares_. In 1657 a theatre was actually built in Florence for the performance of musical comedies. For some reason, however, it did not prove a success, and after a few years was compelled to close its doors. After these first experiments there seems to have been no attempt made to resuscitate opera buffa until the rise of the Neapolitan school in the following century. The genesis of the southern branch of opera buffa may with certainty be traced to the intermezzi, or musical interludes, which were introduced into the course of operas and dramas, probably with the object of relieving the mental strain induced by the effort of following a long serious performance. The popularity of these intermezzi throws a curious light upon the character of Italian audiences at that time. We should think it strange if an audience nowadays refused to sit through 'Hamlet' unless it were diversified by occasional scenes from 'Box and Cox.' As time went on, the proportions and general character of these intermezzi acquired greater importance, but it was not until the eighteenth century was well advanced that one of them was promoted to the rank of an independent opera, and, instead of being performed in scraps between the acts of a tragedy, was given for the first time as a separate work. This honour was accorded to Pergolesi's 'La Serva Padrona,' in 1734, and the great success which it met with everywhere soon caused numberless imitations to spring up, so that in a few years opera buffa in Italy was launched upon a career of triumph.