In music, variation is a formal technique where material (the theme or subject) is repeated in an altered form. The changes may involve harmony, melody, counterpoint, rhythm, timbre, orchestration or any combination of these.
Brahms: Variations & Fugue on a Theme by Handel, Op. 24
The Variations and Fugue on a Theme by Handel, Op. 24, is a work for solo piano written by Johannes Brahms in 1861. It consists of a set of twenty-five variations and a concluding fugue, all based on a theme from George Frideric Handel’s Harpsichord Suite No. 1 in B-flat major, HWV 434.