The compositions of Porpora were predominantly vocal works including approximately fifty operas, a number of oratorios, serenades, cantatas, sacred operas, pieces for teaching (i.e., solfeges), and over one hundred sacred works. He also composed a number of instrumental settings. The vocal compositions of Porpora demonstrate his keen sense of the abilities and limitations of the human voice, a clear cognition of singing requirements and complex ornamentation. He served in a number of different positions during his career. Included in these positions, but not limited to, were posts with the Prince of Hessen-Darmstadt as the master of the chapel (choir master), master of the Incurabli orphanage in Venice, and teaching positions with the conservatories in Naples and Venice. Voice was taught by Porpora throughout most of his life and he also had a distinguished singing voice. His last formal position brought him into the service of the Vienna court. Here he became the instructor of the young Haydn who, for a time, was his accompanist and valet. ~ Keith Johnson, Rovi