The article discusses the German translation of Giuseppe Carpani’s Haydn biography of 1812. While notes on Haydn by the two German biographers Dies and Griesinger are regularly quoted and considered authentic despite the fact that their authors were good observers but not musicians, musicology pays little attention to the third contemporary Haydn biography by the musician Carpani (1752[?]–1825). He was looked upon with distrust and it reflected on him in intellectual circles that his book on Haydn was plagiarized under a pseudonym right after its publication by an author who later acquired world fame as Stendhal.