In 1720 in Italy, opera was largely dictated by the egos of the singers, rather than considering the text, or the composer:
The satirical writer Marcello wrote that the opera composer will hurry or slow down the pace of an aria, according to the caprice of the singers, and will conceal the displeasure which their insolence causes him by the reflection that his reputation, his solvency, and all his interest are in their hands.
… The director will see that all the best songs go to the prima donna, and if it becomes necessary to shorten the opera he will never allow her arias to be cut, but rather other entire scenes. [If a singer] has a scene with another actor, whom he is supposed to address when singing an air, he will take care to pay no attention to him, but will bow to the spectators in the loges, smile at the orchestra and the other players, in order that the audience may clearly understand that he is the Signor Alipi Forconi, Musicoi, and not the Prince Zoroaster, whom he is representing.
All the while the ritornello [the purely instrumental portion] of his air is being played the singer should walk about the stage, take snuff, complain to his friends that he is bad voice, that he has as cold, etc., and while singing his aria he shall take care to remember that at the cadence he may pause as long as he pleases, and make ones, decorations, and ornaments according to his fancy; during which time the leader of the orchestra shall leave his place at hte harpsichord, take a pinch of snuff, and wait until it shall please the singer to finish.
Marek, George (1969) Beethoven: Biography of Genius. London: William Kimber, p. 15.