Here’s an excerpt from Beethoven’s piano sonata no. 5, second movement, measures 13-16, with my analysis in blue (key of Ab major, 2/4 time):
My question is about the notes and chords in the blue box. At first I thought it was a Neapolitan or augmented sixth chord, but it’s not. I’m very curious about the augmented first degrees (A naturals) on relatively strong beats. Is this just chromatic material or is there something functional happening here?