Ernst Kaltenbrunner
The series' creators may have been aware of a 1958 film, "The Two-Headed Spy", in which a high-ranking German general is really a British spy, and has a performer who encodes secret messages into piano accompaniment. The film also features Ernst Kaltenbrunner and Heinrich Müller, whose interactions with the spy are mirrored in "Seventeen Moments of Spring" as well, in a rather surprising resemblance.