* Italian Opera: Haydn was greatly influenced by the Italian opera composers of his time, particularly those of the Neapolitan school. He studied their operas and incorporated many of their stylistic elements into his own compositions, such as the use of recitatives, arias, and ensembles.
* Viennese Classical Music: Haydn was also influenced by the Viennese Classical music tradition of the 18th century. This style was characterized by its clarity, balance, and elegance, and Haydn's music reflects these qualities.
* Church Music: Haydn was a devout Catholic and his religious beliefs had a profound impact on his music. He wrote many sacred works, including masses, oratorios, and cantatas, which are influenced by the music of the Catholic Church.
* Folk Music: Haydn was also influenced by folk music from various regions of Europe. He incorporated folk melodies and rhythms into his own compositions, giving them a lively and earthy quality.
* Composers such as Johann Sebastian Bach, George Frideric Handel, Christoph Willibald Gluck, and Carl Philipp Emanuel Bach: Haydn was exposed to the music of these composers through studying their compositions and attending their concerts. He admired their musical techniques and incorporated some of their ideas into his own music.
* His mentors, Nicola Porpora and Carl Ditters von Dittersdorf: Haydn studied with these two composers during his early career and learned a great deal from them about composition and musical performance.
* The musical environment in Vienna: Vienna was a vibrant musical center during Haydn's time, and he was surrounded by talented musicians and composers. He was able to learn from and collaborate with these musicians, which influenced the development of his musical style.
Haydn's music reflects the synthesis of these various influences, resulting in a unique and distinctive style that has had a lasting impact on Western classical music.