Mozart's Piano Sonata in C Major
Measures 41-48 are in A minor and are harmonized as follows:
m44: V64, V6
m45: i, iidim, III, viidim/iv
m47: N6, V64-5#3
The main focus of this excerpt is on the Neopolitan Sixth in measure 47, formed by a D, F, and B flat. It is approached by a iv chord, and resolves to a V chord thru a 64 chord. As usual with a Neolpolitan Sixth chord, Ra resolves to Ti, thru Do, but instead of Le resolved to Sol, it resolves to Mi, while instead the Fa in the bass resolves to Sol. What is also different is that the left hand switches from Treble Clef to Bass Clef in between the N6 chord and V64-5#3, so there is almost an octave jump between the two lowest notes. To me, this N6 chord represents the peak of the tension of this excerpt. It seems to build through the descending sixteenth notes along with the i-iidim-III-(viidim/iv)-iv harmony, and when you reach the N6 chord, it really sticks out and is rather alarming as you except V to follow iv, but before you know it, it follows and resolves nicely to a V-i cadence.