Franz Schubert's Impromptu Op. 90, No. 2 in A-flat major is a solo piano piece that showcases the composer's mastery of harmony and melodic writing. The piece is characterized by a singing melody, nuanced dynamic shifts, and a range of emotions. This harmonic analysis will explore the piece's chord progressions, tonal harmony, and departures from traditional tonality.

m. 1: I (Ab major) - 3rd inversion (Ab - C - Eb) m. 2: V6/4 (Eb major) - 2nd inversion (Eb - G - Bb) m. 3: I (Ab major) - root position (Ab - C - Eb) m. 4: I (Ab major) - 1st inversion (C - Eb - Ab)

m. 25: V (Eb major) - root position (Eb - G - Bb) m. 27: vii°7/5 (Db7) - 3rd inversion (Db - F - Ab - Bb) m. 29: vi (Gb major) - root position (Gb - Bb - Db)

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.