From the early 18th century until the present day, opera seria as practised by Handel and his contemporaries has been the subject of satire and even derision for its dramatic artifice and virtuosic displays. Close examination of Handel's autograph manuscripts, the librettos upon which they were based, and other contemporary documents, reveal the extent to which Handel was influenced by his singers and their abilities in creating his commercially successful and dramatically effective operas. Drawing on evidence from these sources, the author demonstrates the fact that Handel's singers (such as Francesco Borosini, Margherita Durastanti, Francesca Cuzzoni, and Faustina Bordoni) were the single most important influence on his opera composition during his tenure as composer and music director of the Royal Academy of Music from 1719-28.