Beethoven asks his publisher Steiner to send him the manuscript so that he can correct the proofs of the Sonata op. 90. Apparently Anton Diabelli had found some mistakes. (In 1815 he was still an employee at the Steiner publishing house and was a reliable and feared proof reader.) Beethoven is sure that he did not make the mistakes but that they occurred when it was being engraved. In order to be able to check the proofs against the manuscript he needs the latter back.
In 1815 Beethoven still had a friendly relationship with Steiner, as shown in this short letter. Anton Diabelli refers to Beethoven - as he often does - as "Diabolus [devil] Diabelli". In this case he even adds a rank - "erster Diabolus des Reichs" ("the empire's first Diabolus"). Steiner is given his usual title "Generalleutnant" (abbreviated to "g.l.") and Beethoven refers to himself as "Generalissimus" ("g-s"), as usual. His parting wish "Go to hell Herr g.l. and God be with you." also shows the heartiness of their relationship. Four years later Beethoven wrote a canon (WoO 173) for Steiner using the same text; similar texts are also used in the canons for Abbé Stadler and Ignaz Schuppanzigh.
