Leo Leonardo was only a `relatively' prolific composer when one considers that many of his compositions were newer versions of his earlier works. He composed in a number of genres including the serious opera, comic opera, chamber cantatas, dramas, oratorios, and overtures. The latter compositions were very important in the development of the pre-Classical symphony as they were not arranged simply as instrumental concertos. Within the content of his operas was the addition of the chorus, a development that influenced Neapolitan opera for years to come. Leo's compositions were quite diverse and the most technically advanced in comparison to his contemporaries, Vinci and Hasse; however, he lacked the ease with which they composed and was forced under lock and key to complete an opera for which he was commissioned. His sacred compositions advanced the use of a choral cantus firmi and he restructured the idiom through the use of counterpoint and orchestral accompaniment. Leo's operas included "Il Pisistrato," "Sofonisba," and "Caio Gracco," while oratorios included "S Elena al Calvario," and "La morte de Abele." ~ Keith Johnson, Rovi