#Here#s a sonata that will challenge pianists and that one will be able to play in 50 years#: thus Beethoven is said to have written to his publisher Artaria regarding his mighty #Hammerklavier# Sonata Op.106. Given its monumental scale and extreme musical and pianistic demands, the term #Grande Sonate# seems almost an understatement. Dedicated to Archduke Rudolph of Austria, this sonata is famous not least for the seemingly unplayable autograph metronome marks in the opening movement and final fugue # a matter on which the editor offers a new explanation. Nothing is uncomplicated in this pinnacle of the classical-romantic piano sonata, composed in #adverse circumstances# from 1817 to 1819. Even the sources pose supreme editorial challenges.