Beethoven

The chord structure of this excerpt from Beethoven's Piano Sonata in C is as follows: m.41-IV, m.42-I^6/4 and V^7, m.43-I, m.44-V^4/2, m.45-I^6, m.46-IV^6 and Fr^6, m.47-V, m.48-V^4/2, m.49-I^6 and (V^6)/VI, m.50-VI and V, m.51-I.

The augmented sixth chord is in measure 46 and is a French Augmented Sixth Chord. It is approached by a IV^6 chord and is resolved to a root position V chord. The base of the IV^6 chord moves up a half step to make the me of the Fr^6 chord, the Eb remains the same, and the Ab moves up a half step for the Fi of the Fr^6 chord. The Fi of the Fr^6 chord moves up to Sol for the V chord, the Do moves down to Ti, the Le moves down to Sol, and the Re remains as it is for the V chord. This is a normal type of approach and resolution. The chord in measure 49 is not an augmented Sixth chord.