It was originally the genre name for piano solo music, and was later used for solo music for other instruments. It is an improvised instrumental piece, often composed of exciting passages and profound lyrical passages, so most of them are complex. The name Impromptu was coined by Schubert. It has no obvious genre characteristics and generally refers to music composed temporarily by the composer without any prior preparation, that is, it is often an expression of temporary inspiration. The music is composed of three sections: the first section is in C-sharp minor, with the right and left hands joining together rapidly in different rhythms, giving people an illusion; the middle section is in D-flat major, with a beautiful cantabile melody. The listener is transported into a beautiful world of fantasy; and then returned to the first paragraph. The melody in the middle section at the end is repeated in the bass, as if the fantasy world is still appearing and disappearing, creating a lingering effect.