Winton Dean

“The falling-off in quality of the later Academy operas, which is a matter of dramatic unity rather than musical invention, was almost certainly due to the presence of two jealous prima donnas each anxious to outshine the other. In order to prepare the lists for this contest, the libretto had to be manipulated so that the two parts had equal prominence, vocally if not dramatically. It may be evidence of Handel's tact that he wrote only one duet for Cuzzoni and Faustina, a short piece in Alessandro, the first opera in which they sang together, just as in his whole career he composed a single duet for two castrati. This was in Tamerlano; and he cut it before performance. These animals were too dangerous to be put in the same cage.”
― Winton Dean, Handel and the Opera Seria