A deviation from a theme that uses the same bass pattern or harmonic progression that the theme used, and usually having the same number of measures as the theme. Generally, a variation is played after a theme with the variation being slightly more ornate; in several cases there are many variations upon a single theme. Variations are often used as accompaniments to songs that are several verses long, or as dance music. In both cases, the repeating structure is beneficial to the nature of the function.