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 vocal 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 ideas and evidence from these sources, this study demonstrates the fact that Handel's singers were the single most important influence in his opera composition during his tenure as composer and music director of the Royal Academy of Music from 1719-28.