At the prestigious IGS 2023 Conference in Évora, Portugal, we revealed a bombshell that shakes the foundations of Mozart’s legacy. Our research uncovered that the famous thematic catalogue, long attributed to the composer, is a forgery. Using cutting-edge technology and painstaking forensic handwriting analysis, we have shown that the document was most likely fabricated after Mozart’s death, shattering long-held beliefs about the authenticity of his works.

Mozart’s wife, Constanze, has long been credited with preserving and authenticating this catalogue, yet the document never appeared during Mozart’s life. Only after his death did it emerge, forming the basis for the sales of his unattributed works. This raises significant doubts about Constanze’s role and the narrative surrounding Mozart’s catalogue. As we examine in detail in Mozart: The Construction of a Genius, this catalogue played a crucial part in elevating Mozart’s posthumous reputation, though it is now clear that its authenticity cannot be trusted.

Our bespoke C# software analysed hundreds of characters, comparing the writing in the catalogue with authentic manuscripts and letters from Mozart’s hand. The results were astounding—discrepancies in handwriting, clef shapes, and even the ink used, which was inconsistent with Mozart’s manuscripts. Particularly telling were examples like the word “Bassi,” whose form in the catalogue contrasts starkly with known examples from Mozart’s compositions. The watermarks also provided another clue, revealing connections to documents dated after Mozart’s death in 1791.

This forgery goes beyond simple discrepancies; it alters how we view Mozart’s works catalogued between 1784 and 1791, questioning the legitimacy of many pieces previously believed to be authentic. As explored in our book Mozart: The Construction of a Genius, this discovery raises deeper questions about the image of Mozart that has been manipulated over the centuries for various purposes—ranging from Constanze’s financial gain to nationalistic symbolism and commercialisation of the composer’s legacy.

The scholarly paper A Questionable Catalogue, presented at IGS 2023, corroborates these findings with compelling forensic evidence, adding weight to the notion that the thematic catalogue is not what it appears to be.

This discovery changes everything, forcing scholars to revisit the foundation of Mozart’s legacy. What other elements of the Mozart myth are based on unreliable sources? Our research opens the door to rethinking not just this document but the entire narrative around one of history’s most revered composers.