The real heart of this Sonata is its finale. It opens with a recitative, full of changes of tempo and figuration, before the Adagio proper gets under way - a klagender Gesang (tearful song) over incessant semiquaver chords. This leads straight into a three-voice Allegro fugue, and the genius of Beethoven's scheme becomes clear when the fugue subject recalls the outline of the opening melody of the first movement - a subtle association by suggestion rather than outright imitation.
If you take a piece like Op. 110 of Beethoven, that whole introduction to the slow movement, in the space of something like six measures, are some 22 or 23 different instructions by Beethoven on how to play those six bars. And each time you play, it is an opportunity to get closer to what you think is the combined intention of that. I don’t think of that as surpassing Beethoven. These people are some of the most singular in the history of mankind. These are giants of human expression, of human awareness, and I think it would be a little arrogant to think of going beyond them.
The most obvious example is Op. 110, which has a kind of narrative progression, from the relative calm and serenity of the opening movement, to the brusque and almost savage second movement, which seems to take place in a tavern. Part 3, with its aria and fugue, certainly gives a feeling of transformation — from suffering to a kind of exultation at the end.
Richard Goode, "Pianist Richard Goode: Adventures in Beethoven" by Niels Swinkels (April 2, 2013)