Mozart's 1778 stay in Paris was pretty much a total washout. Instead of making his name there as a composer, he was rebuffed and ignored. His mother died. He was cold and starving. And people kept stiffing him for his work.
While in France, Mozart had to take on private students to pay the bills. One of those students was the daughter of Adrien-Louis de Bonnières, the Duc de Guînes. The duke was nonchalant about compensating the struggling Mozart for his work. On July 31, 1778, Mozart wrote his father of one such unsavory episode.