Impromptu Op. 90, No. 2, is written in the key of A-flat major, with a tempo marking of "Allegretto." The piece follows a modified sonata form, comprising an exposition, development, and recapitulation. The structure can be outlined as follows:
This pivot is the cornerstone of the piece’s harmonic architecture. The relationship between the original key of E-flat major (6 flats) and the new key of B minor (2 sharps) is a . By journeying through the "flat side" of the circle of fifths to achieve a key on the "sharp side," Schubert liberates harmony from diatonic function, creating a startling and dramatic shift in color and mood. schubert impromptu op 90 no 2 harmonic analysis
The Trio (Section B) is one of the most famous examples of Schubert’s bold harmonic language. It shifts to . Impromptu Op