Schubert's first impromptu, in C minor (op. 90, no. 1), and the finale of his last sonata, in B♭ major (D. 960), could hardly be more different. Yet these two movements might strike a casual listener as beginning in much the same way (ex. 1.1a–b). In each, a forcefully struck, seemingly portentous G sets the stage for a C-minor melodic beginning that is marked motivically by repeated notes and keeps close to its tonic. In each, as well, the abruptness and the gestural isolation of the opening G suggest something other than a simple beginning: the G commands attention, like a symbolic call to whose meaning the ensuing melody provides the first clues; it invokes a setting from which that melody is heard as an emanation.
In relation to these opening Gs, however, and to the initially undisclosed meaning to which these Gs allude, the impromptu and the finale soon reveal themselves as opposites. In the second period of the impromptu, each phrase seems to begin in E♭, the relative major, but then falls back into C minor for its cadence (ex. 1.1b, mm. 10–17). The music progresses—in a sense, fails to progress—as if the opening dramatization of G, C minor's dominant, has revealed that dominant as invested not merely with its normal capacities for tonal hierarchization and resolution but also with a power to hold the music in its thrall. 1 To be sure, the music digresses through a kind of echo into a contrasting episode in A♭ major (ex. 1.1c, mm. 40ff.)—this is the second, or B, section of its five-part, ABA'B'A" form—but only with such contrasts of rhythm, texture, harmony, and phrase structure as to embody an