I. Allegro (第一乐章 快板)-Jean-Bernard Pommier

The first movement opens with a series of fortissimo B♭-major chords, which form much of the basis of the first subject. After the first subject is spun out for a while, the opening set of fortissimo chords are stated again, this time followed by a similar rhythm on the unexpected chord of D major. This ushers in the more lyrical second subject in the submediant (that is, a minor third below the tonic), G major. A third and final musical subject appears after this, which hints at G minor by chromatic alterations of the third scale degree, as well as the minor subdominant C minor. The exposition ends with a largely stepwise figure in the treble clef in a high register, while the left hand moves in an octave-outlining accompaniment in eighth notes. The development section opens with a statement of this final figure, except with alterations from the major subdominant to the minor, which fluidly modulates to E♭ major. Directly after, the exposition's first subject is composed in fugato and features an incredible display of musical development. The fugato ends with a section featuring non-fugal imitation between registers, eventually resounding in repeated D-major chords. The final section of the development begins with a chromatic alteration of D♮ to D♯. The music progresses to the alien key of B major, in which the third and first subjects of the exposition are played. The retransition is brought about by a sequence of rising intervals that get progressively higher, until the first theme is stated again in the home key of B♭, signalling the beginning of the recapitulation. In keeping with Beethoven's exploration of the potentials of sonata form, the recapitulation avoids a full harmonic return to B♭ major until long after the return to the first theme. The coda repetitively cites motives from the opening statement over a shimmering pedal point and disappears into pianississimo until two fortissimo B♭ major chords conclude the movement.