Beethoven was fifty. Though completely deaf, the ageing composer stood at the height of his creative powers. While rumours circulated that he was ‘written out’ since few of his pieces had recently been published, Beethoven was sketching several gigantic new works: the Missa Solemnis, the ‘Diabelli’ Variations, and the Ninth Symphony. Then, in the spring of 1820, he turned for the last time in his career to his favourite medium of the piano sonata. Between 1820 and 1822, he repeatedly set the Mass aside in order to write a trilogy of piano sonatas for the publisher Adolf Schlesinger, which became one of the outstanding achievements of Beethoven’s late style.