Composed in 1809 and published in 1810. Dedicated to Count Brunswick. This piece can be said to condense the characteristics of toccatas and fantasies for harpsichord, exemplified by J.S. Bach, and the free fantasies of C.P.E. Bach. For example, its features include an improvisatory character, connections made by motifs of differing characters, and changing keys and tempos. Many keys are intermingled, such as G minor, F minor, D-flat major, B major, D minor, D major, B minor, B major, C major... Although this piece is sometimes introduced as "Fantasia in G minor," only the opening few measures are actually in G minor, so it might not be entirely accurate to call it a "piece in G minor."

The figuration alternates between improvisatory and metric/melodic passages. For example, the former includes rapid ascending/descending runs and fine tuplets, while the latter consists of smooth, slurred chordal figures. The tempo also mixes fast and slow sections; the "fast" parts convey a passionate tension, while the "slow" parts evoke light and shadow or tranquility through harmonic changes.