Rossini, in fact, introduced into serious opera the forms which comic opera already possessed. The parts were at that time differently distributed in _opera seria_ and _opera buffa_; and in the latter less restricted style the bass singer was not as a matter of course kept in the background. _Tancredi_ was the first serious opera in which a certain prominence was given to the bass, though it was not until some years later--in _Otello_, 1816, in _La Gazza Ladra_, 1817, and in _Mosè_, 1818--that Rossini ventured to entrust bass singers with leading parts. _Opera seria_, when Rossini was beginning his career, was governed by rules as strict, as formal, and as thoroughly conventional as those which gave so much artificiality and so much dulness to the classical drama of France. The company for comic opera consisted of the _primo buffo_ (tenor), _prima buffa_, _buffo caricato_ (bass), _seconda buffa_, and _ultima parte_ (bass). The company for serious opera was made up of the _primo uomo_ (soprano), _prima donna_, and tenor, the _secondo uomo_ (soprano), _seconda donna_, and _ultima parte_ (bass); and in serious opera the _ultima parte_ was not only kept in the background, but, except in concerted pieces, was scarcely ever heard. As a solo singer, the bass in serious opera had no existence. Gradually Rossini brought him forward, until he became at last as prominent as the tenor, or even more so. In _Semiramide_, for instance, the principal male character is Assur. In _Tancredi_, from which _Semiramide_ is separated by an interval of ten years, the bass has little to do. He already, however, possesses an importance which was denied to him in the serious operas of Rossini's predecessors. In _Tancredi_, again, the composer introduces concerted pieces in situations where, had the ancient method been followed, there would have been only monologues. In these concerted pieces, moreover, the dramatic action is kept up, whereas the endless monologues and long sequences of airs which gave such character as they possessed to the operas of Rossini's immediate predecessors had the effect of delaying it. To musical reformers of a later period Rossini himself seemed to insert songs in his operas merely for the sake of singing, and greatly to the injury of the drama. But he diminished considerably the number of formal airs which, until he began to write, were included as a matter of course in every opera. He increased the number of characters, and made, for the first time in Italian opera, a free use of the chorus, which in the works of the old school plays quite a subordinate part and has no dramatic functions assigned to it at all.