and melodic tics; the use of onomatopoeia and interjections; the exclusion of castrati. In the second half of the 18th century comic opera owed its success to the collaboration between the playwright Carlo Goldoni and the composer Baldassare Galuppi. Thanks to Galuppi, comic opera acquired much more dignity than it had during the days of the intermezzo. Operas were now divided into two or three acts, creating libretti for works of a substantially greater length, which differed significantly from those of the early 18th century in the complexity of their plots and the psychology of their characters. These now included some serious figures instead of exaggerated caricatures and the operas had plots which focused on the conflict between the social classes as well as including self-referential ideas. Goldoni and Galuppi's most famous work together is Il filosofo di campagna (1754). The collaboration between Goldoni and another famous composer Niccolò Piccinni produced with La Cecchina (1760) another new genre: opera semiseria. This had two buffo characters, two nobles and two "in between" characters. The one-act farsa had a significant influence on the development of comic opera. This was a type of musical drama initially considered as a condensed version of a longer comic opera, but over time it became a genre in its own right. It was characterised by: vocal virtuosity; a more refined use of the orchestra; the great importance given to the production; the presence of misunderstandings and surprises in the course of the drama. Gluck's reforms and Mozart Opera seria had its weaknesses and critics; a taste for embellishment on behalf of the superbly trained singers, and the use of spectacle as a replacement for dramatic purity and unity drew attacks. Francesco Algarotti's Essay on the Opera (1755) proved to be an inspiration for Christoph Willibald Gluck's reforms. He advocated that opera seria had to return to basics and that all the various elements—music (both instrumental and vocal), ballet, and staging—must be subservient to the overriding drama. Several composers of the period, including Niccolò Jommelli and Tommaso Traetta, attempted to put these ideals into practice. In 1765 Melchior Grimm published "Poème lyrique", an influential article for the Encyclopédie on lyric and opera librettos. The first to really succeed and to leave a permanent imprint upon the history of opera, however, was Gluck. Gluck tried to achieve a "beautiful simplicity". This is illustrated in the first of his "reform"