Daniel Barenboim performing the Beethoven piano sonata no. 29, opus 106, The Hammerklavier Sonata. The Hammerklavier is widely considered to be one of the most important works of the composer's third period and one of the great piano sonatas. It is considered Beethoven's single most difficult composition for the piano, with the possible exception of the Diabelli Variations, and it remains one of the most challenging solo works in the entire piano repertoire.
Part 1 and part 2 of a lecture by András Schiff on Beethoven's piano sonata op. 106.