 The Allegro begins with a theme in G major built around a quarter-eighth-eighth note motif.21 measures of nonstop sixteenth-notes build from "piano" to a powerful "forte" as the piece arrives at a hemiola-infused G major restatement of the Introduction's opening fanfare.Instead of a development section as would be expected in traditional sonata form, a new theme is introduced, a vigorous fugue in which the piece returns to the opening key of G minor.