"Impromptu" originates from Latin, meaning "unprepared." It is said that the term was first used simultaneously by two composers for their own works by chance in 1822. As a musical genre, the impromptu has little relation to improvisation as a performance technique. It simply refers to a piece of music that reflects an improvisatory atmosphere, and it is a musical genre that emerged in the 19th century or later. (While the idea of improvisatory music itself is by no means unique to the 19th century, it was previously referred to by various names such as toccata and capriccio.)

In the first half of the 19th century, the tradition of the impromptu largely followed two main currents. One involved continuous variations on popular opera arias or folk melodies, exemplified by Czerny, Kalkbrenner, and also some fine works by Liszt. The other comprised lyrical musical content without a specific form, represented by Voříšek and Marschner, who are said to have first used the term, as well as Schubert's impromptus. However, even if the form is not fixed, many exhibit an A-B-A arch structure.

Chopin inherited the tradition linked to Schubert, leaving behind the Fantaisie-Impromptu and three Impromptus during his middle creative period. All of them have a clear arch form, with the middle section designated as "sostenuto."

At first glance, the main theme of Impromptu No. 2 does not appear particularly "improvisatory." The rhythmic pulse is clear, with a memorable and bright melody used in the A section, and a dignified melody in the Sostenuto. However, as early as measure 19, a subdivision of the motif occurs during the theme's establishment. And when the recapitulation of the theme begins at measure 61, one realizes that this piece incorporates the tradition of variation. The entire texture is disrupted by the elusive left-hand accompaniment, and the right hand is also divided into triplets in the latter half. Furthermore, this section leaps from A minor to F-sharp major with almost no warning, and such sudden changes in color are calculated as an effect of variation. From measure 82, a brilliant passage work spanning 19 measures begins, which can be considered an expansion of the 20-note figure from the opening measure 17. However, the final nine measures are faithfully recapitulated, creating a momentary sense of relief from the return of the theme. It should be noted that marking the last two notes fortissimo is an instruction based on the first edition. In Chopin's sketch and the edition published in England, fortissimo is marked only on the final note of measure 110.