Part 2, movement 3, Theme - Var. 4. Nate Koch, piano. You can find a playlist of the complete sonata here:
http://www.youtube.com/playlist?list=PLBC63FABF85CB9C4A&feature=view_all
Beethoven was a master of variation, and I think that this theme and variations (parts 2 and 3 of this recording) is one of his most sublime sets.
The theme (0:02), marked to be played "with the innermost feeling," is a stately, noble, and piercingly beautiful late Beethoven melody that looks back at a full life with no regret.
Variation 1 (2:23) anticipates a viennese waltz, in 3/4 time and draped with delicate grace notes. But Beethoven never allows you to feel completely comfortable, as inexplicable groans occasionally well up from the bass.
Variation 2 (4:33) has contrasting sections of light, separated notes, playfully outlining the harmonies of the theme, and more passionate, forward moving sections of trills and oddly syncopated rhythms.
Variation 3 (6:10) is short and virtuosic, with fast scaler runs, like a lively two-part invention.
Variation 4 (6:41) is one of the most expressive of the variations. The first instances of triplets in the movement create a relaxed, lilting feeling, though as usual it is quickly disturbed by waves of deeper emotion. At 8:07 a spooky whistle ushers in the second half of the variation, that crescendos to one of the emotional climaxes of the movement, marked to be played "the loudest."