Verdi preferred to choose the opera’s subject and to pull it from a successful spoken drama from writers such as Shakespeare and Hugo. Verdi also composed with certain singers in mind, creating vocal parts that would best fit the individual’s voice. He typically would wait to complete the orchestration until after rehearsals began.
In his famous Rigoletto, Verdi uses various styles of singing to depict the main characters. The hunchback Rigoletto does not have a clear aria while the Duke of Mantua sings in a tuneful manner. Gilda alternates between both styles. Here is a clip from Rigoletto: