Which composers and music theory books did Joseph Haydn study on his own?

After Joseph Haydn was expelled from the choir school at St. Stephen’s Cathedral, he was left to his own devices and undertook an arduous course of self-instruction to compensate for the lack of formal theory training he received as a youth.12

During this period of self-study, Haydn focused on the following:

• Musical Works: He notably studied the compositions of Carl Philipp Emanuel Bach, whose expressive style significantly influenced his development.13
• Music Theory Manuals: Haydn studied leading manuals of musical theory to improve his craft. While the specific titles of all these manuals are not always listed, historical records confirm he studied the influential counterpoint textbook Gradus ad Parnassum by Johann Joseph Fux.14

Through this persistent self-instruction and his later work with the Italian composer Nicola Porpora, who corrected his compositions, Haydn successfully bridged the gaps in his early education.1