Variation
Variation form involves the repetition of a theme in changed versions. It is possible to vary the melody, its rhythm and its harmony, or to vary by addition. Early variation forms include the chaconne and the passacaglia, originally dances based on variations on a simple repeated bass or chordal pattern. Later examples of variations include Elgar's well known Enigma Variations and the Handel, Haydn and Paganini Variations of Brahms.