Harmonic Analysis - C Section

The 'C' section is fairly tricky harmonically. This is where Beethoven incorporates actual key changes with the use of modal mixture. In the last two bars of the second 'A' section, Beethoven switches to c minor. This 4-5 bar switch allows him to easily move to the key of Ab Major in measures 84 and 85. It is not quite clear where Beethoven actually moves to Ab, as 84 and 85 can either be the VI and Neapolitan in c minor or I and IV in Ab. He remains in Ab until around measure 95. This time is a fairly obvious transition to a minor, as measure 95 is either the bVI in Ab or the VI in a. A perfect use of modal mixture to move between two completely different keys.