The main difference between Opera and the previous polyphonic vocal music is the unique melodic line, resulting from the merging of bass and singing. In polyphonic music different vocal lines work independently, overlapping one another and making a text often incomprehensible. Opera instead offered a new way for making words expressive and intelligible, by creating a single melodic line, supported by an accompaniment.
Monteverdi reinvents vocal music as a new relationship between the composer and his audience, using to that end his melodies of unprecedented expressivity. He creates modern opera as the public’s right to a performance he can understand, appreciate, being moved or laugh at.
Rossini wrote his first opera, Demetrio e Polibio in 1806 not even fifteen. His official debut was in Venice in 1810 with the opera La Cambiale di Matrimonio. In the following two decades Rossini composed 39 operas, 4 or 5 new ones per year, with some controversial premieres, such as the Barber of Seville legendary fiasco in Rome in 1816 and some extraordinary successes: La Gazza Ladra, Zelmira and Semiramide, the last opera premiered in Italy in 1823.