Beethoven's hearing loss did not prevent him from composing music, but it made playing at concerts—an important source of income at this phase of his life—increasingly difficult. (It also contributed substantially to his social withdrawal.) Czerny remarked that Beethoven could still hear speech and music normally until 1812. But in April and May 1814, playing in his Piano Trio, Op. 97 (known as the ’’Archduke’’), he made his last public appearances as a soloist. The composer Louis Spohr noted: “the piano was badly out of tune, which Beethoven minded little since he did not hear it there was scarcely anything left of the virtuosity of the artist I was deeply saddened.” From 1814 onwards Beethoven used for conversation ear-trumpets designed by Johann Nepomuk Maelzel, and a number of these are on display at the Beethoven-Haus in Bonn.