Foundation Musick's Monument
Reichsfreiherr Johann Baptist Franz Berchtold zu Sonnenburg (* 22. Oktober 1736 in der Stadt Salzburg; † 26. Februar 1801 in St. Gilgen) war Pfleger von St. Gilgen und Ehemann von Maria Anna Walburga Ignatia Mozart, genannt Nannerl.
Eventually, on 23 August 1784 Maria Anna Walburga Ignatia Mozart, aged 33, married a magistrate named Johann Baptist Franz Freiherr von Berchtold zu Sonnenburg (1736–1801),and settled with him in St. Gilgen, a village in Austria about 29 km[ east of the Mozart family home in Salzburg. The wedding was attended by Leopold, Katherl Gilowsky, some others, but not Wolfgang.
Berchtold lived in St. Gilgen because his occupation was "Pfleger," i.e. the representative of the Salzburg government in the area; it was a demanding position. This, curiously, had been also the position of Marianne's maternal grandfather Wolfgang Nikolaus Pertl, from 1716 to 1724.The government had built a substantial residence and headquarters for the Pfleger in 1720, and this is the home (where her late mother had spent her first four years) into which Maria Anna moved on her marriage.