Beethoven writes to his publisher Steiner, asking him to send the "Diabolus" Anton Diabelli to him so that they can discuss the arrangement of op. 91 for "Turkish music".
At this time Diabelli was an employee at Steiner's publishing house. Beethoven's nickname "Diabolus" (devil), a parody of the name Diabelli, was his usual but not at all nastily meant form of address for the employee, whom he greatly respected.
