When was the Austrian pianist which Stefan Knüpfer worked with born 
Pianomania:  The film presents Stefan Knüpfer, a virtuoso piano tuner from the piano company Steinway & Sons, in his work with pianists such as Lang Lang, Alfred Brendel and Pierre-Laurent Aimard. Alfred Brendel: Alfred Brendel KBE (born 5 January 1931) is an Austrian pianist, poet and author, known particularly for his performances of Mozart, Schubert, Schoenberg, and especially Beethoven.
5 January 1931