The B section begins with a new theme in the key of E-flat major (V of Ab major). The harmony becomes more complex, with a series of secondary dominants and borrowed chords:
The Impromptu Op. 90, No. 2 is structured in a modified A-B-A form. The A sections are in the tonic key of A-flat major, while the B section modulates to a series of related keys. schubert impromptu op 90 no 2 harmonic analysis
The piece begins in A-flat major, with a gentle, lilting melody in the right hand accompanied by a steady, pulsing rhythm in the left hand. The chord progression is largely diatonic, with a I-V6/4-I progression in the first four measures: The B section begins with a new theme