Telemann’s Beschreibung der Augen-Orgel oder des Augen-Clavicimbels (Hamburg, 1739) has generally been interpreted as a commentary on the “clavecin pour les yeux” invented by the French Jesuit mathematician and philosopher Louis-Bertrand Castel (1688–1757). This publication was widely received as an influential contribution to one of the liveliest debates of the Enlightenment – the intense controversy over Castel’s theories of sound-color analogy. A look into the genesis and influence of Telemann’s Beschreibung reveals the source of its text and exposes a bilingual tableau of intellectual loyalties and rivalries. Among the luminaries who weighed in were Voltaire, Rameau, Mizler, and Mattheson, whose unpublished manuscript on the subject includes the same French letter that inspired Telemann. This essay confirms that the letter’s author was Castel himself. Telemann’s text was a fairly literal translation, but it was quickly and anonymously translated back into French by Castel, who deceptively published it as though it had Telemann’s imprimatur. Due to the composer’s celebrity, this text, as erroneously attributed to him, appeared in no fewer than eight versions between the years 1739 and 1757 in French, German, and Latin.