Although born in Austria, Haydn was of pure German stock. He was one of the most important figures in the development of the Classical style in music during the 18th century. He helped establish the forms for the string quartet and the symphony. Haydn was an extremely prolific composer. His total output was vast and includes the following: 108 symphonies; 68 string quartets; 32 divertimenti for small orchestra; 126 trios for baryton, viola, and cello; 29 trios for piano, violin, and cello; 21 trios for two violins and cello; 47 piano sonatas; about 20 operas; 14 masses; and 6 oratorios amongst many other musical works.

Haydn's achievement was long confused by the fact that an enormous number of works were wrongly attributed to him, and it was not until the 1950s that musicological research was able to pare this staggering amount of spurious attributions from Haydn's recognised output. Work on a definitive catalogue of his compositions continued into the late 20th century.

Haydn was a true representative of the Enlightenment. His optimistic approach to life; his striving for a balance between intellect and emotion; his sense of moderation, leading to the avoidance of strongly discordant moods; all these found superb expression in his music and were appreciated by his contemporaries. Music lovers also found irresistible the nobility and deceptive simplicity of his idiom, sparked by delightful outbreaks of humour. The gaiety and naturalness of Haydn's music held less appeal to the Romantic era of the 19th century, however, when dark, complex moods and ambivalent emotions were being explored in music. But in the 20th century there was a re-evaluation of Haydn's work, and his outstanding thematic elaborations, the originality of his modulations, and the artistry and superb craftsmanship of his orchestration were again appreciated in full measure.