Mozart and the Four-Hand Sonata K. 19d
Alan Tyson was the first to solve a persistent Mozart riddle: the priority and dating of the earliest editions of the sonata for four hands, K. 19d. As he showed, the Paris print published by de Roullede in February 1788 not only preceded by a year and a half Andrew's London edition of August 1789, but it also served as the basis for the later print.1 By establishing the priority of the French edition, Tyson brought sharper definition both to our knowledge of Mozart's earliest compositions, and to the history of keyboard music in general. K. 19d is among the earliest sonatas composed for keyboard duet and it apparently shows Mozart not only as a precocious talent, but as an innovator as well.
Yet the dating of the early editions of K. 19d is not the only problem posed by the sonata. For although contemporary documents leave no doubt that Mozart and his sister performed keyboard duets in London in 1765, the identification of the works, and in particular Mozart's possible authorship of them, has never been settled.
The earliest reference to Mozart's composition of a four-hand sonata derives from a letter cited in the Mozart biography of Georg Nikolaus von Nissen, Constanze Mozart's second husband. According to Nissen, Leopold Mozart wrote to Salzburg on 9 July 1765: 'In London Wolfgangerl composed his first work for four hands. Until that time a sonata for four hands had never been composed.'2 This passage is not without problems: not only is the original letter lost, but the sentences do not occur in the earliest____________________