Variation, in music, is the technique of adding to or changing some element of a composition. The technique is often called theme and variations. Composers take a theme—either their own or that of another composer—and write a set of variations on that theme.
The number of variations that can be written on a theme is limited only by the composer’s imagination. The main types are melodic variation and harmonic variation. In melodic variation, the melody is altered but remains recognizable. For example, it may be speeded up or slowed down, or played in different meters. In harmonic variation, the composer may completely change the harmony, but the basic melody is preserved.
Spanish and English composers originated the theme and variations form in the 1500’s. Since that time, most composers have used the form, either for independent pieces or as sections of sonatas, symphonies, and other large-scale instrumental works.
