variation

A variation takes a theme and transforms it while preserving something essential — usually the harmonic structure, the melody, or the form. The art of variation lies in balancing familiarity (the listener must recognise the theme) with novelty (each variation must offer something new). Variations can change almost anything: rhythm, tempo, key, mode, texture, dynamics, or character. A theme in C major might appear as a minor-key variation, a virtuosic fast variation, a lyrical slow variation, and a triumphant final variation. The form has attracted the greatest composers — Bach's Goldberg Variations, Beethoven's Diabelli Variations, and Brahms's Variations on a Theme by Haydn are landmark works.