The letter, dated 20 Dec 1780, refers to Idomeneo, which premiered in Munich on 29 Jan 1781. “Faßnacht” refers to the end of the carnival season on the day before Ash Wednesday, which fell on 28 Feb in 1781. The writer of the letter advises the recipient to travel to Munich during the upcoming carnival season: “...because you are also a music lover; for young Mozart of Salzburg will set a new opera to music; I have no doubt that it will receive universal applause, because one can expect nothing else from such a born artist.”
The title page of Briefe eines Reisenden does not name an author, but Wurzbach attributes the book to the Benedictine Dominicus Beck (1732–1791), a mathematician and physicist, who was born in Opfingen an der Donau and died in Salzburg. From 1762 to 1764, Beck was professor of theoretical philosophy in Salzburg, and he remained in Salzburg from 1766 to the end of his life, where he was, among other things, an advisor to Archbishop Hieronymus Colloredo on the construction of buildings and waterworks. He is also said to have built the first lightning rod (Blitzableiter) in Salzburg.
The frontispiece to Briefe eines Reisenden includes an engraving of Beck. His name is not given, but the caption gives his birthdate: “N. Æ. CDDCCXXXII / DIE XXVII SEPT” (27 Sep 1732).