

The earliest at which it is likely they would have met is 22 and 23 December 1783, at a performance sponsored by the Vienna Tonkünstler-Societät, a charitable organization for musicians.

Meeting Īs Jones notes, there were various points in the 1770s and early 1780s when Haydn and Mozart might have met, Haydn visiting Vienna from his normal work venues of Esterháza and Eisenstadt, Mozart from Salzburg. In these periods it was often feasible for Haydn to make brief visits to Vienna, about 40 km away. During the winter months, the Prince moved to the ancestral palace of his family in Eisenstadt, bringing Haydn with him. Haydn's presence was required most of the time at the palace of Eszterháza in Hungary some distance from Vienna, where his employer and patron Prince Nikolaus Esterházy preferred to live. The two composers probably weren't able to meet until after Mozart's permanent relocation to Vienna in 1781.

168–173 the 17-year-old Mozart wrote during a 1773 visit to Vienna. His six string quartets Opus 20 (1772), called the "Sun" Quartets from the drawing of the sun on the cover of the first edition, were widely circulated and are conjectured (for instance, by Charles Rosen) to have been the inspiration for the six early string quartets K. Haydn was already a fairly well-known young composer in Mozart's childhood. Six string quartets by Mozart are dedicated to Haydn (K. Their relationship is not very well documented, but the evidence that they enjoyed each other's company is strong. The composers Wolfgang Amadeus Mozart (1756–1791) and Joseph Haydn (1732–1809) were friends.
