Symphony No. 35 in D major, K. 385, also known as the Haffner Symphony, was composed by Wolfgang Amadeus Mozart in 1782. It was commissioned by the Haffners, a prominent Salzburg family, for the occasion of the ennoblement of Sigmund Haffner the Younger. The Haffner Symphony should not be confused with the eight-movement Haffner Serenade, another piece Mozart wrote on commission from the same family in 1776.
The Haffner Symphony did not start its life as a symphony, but rather as a serenade to be used as background music for the ennoblement of Sigmund Haffner. The Mozarts knew the Haffners through Sigmund Haffner's father, Sigmund Haffner the Elder, who had been mayor of Salzburg and who had helped them out on their early tours of Europe. The elder Haffner died in 1772, but the families remained in contact. In 1776, the younger Haffner commissioned a serenade for the wedding of Marie Elizabeth Haffner to Franz Xavier Spath. This work became the famous Haffner Serenade, which was so successful that, when the younger Sigmund Haffner was to be ennobled, it was only natural that Mozart was called upon to write the music for the occasion. The request to write music actually came via Mozart's father on 20 July 1782 when Mozart had no spare time. Mozart was "up to his eyeballs with work". Not only was he teaching, but he also had to rearrange the score of his opera Die Entführung aus dem Serail before July 28. In addition to these demands, his proposed marriage to Constanze Weber was threatened by a number of complications, including moving to a house on the Hohe Brücke in Vienna. Nevertheless, Mozart worked on the music, and sent it through section by section to his father. What Mozart wrote at this time was a new serenade – a completely different work from the serenade presented four years earlier – with an introductory march and two minuets. According to historical evidence, it is quite possible that Mozart did not actually meet his father's deadline to have the music completed by Sigmund Haffner's ennoblement. Mozart later reworked this music into what we now know as the Haffner Symphony.