Theme and variations

Theme and variations is a form in which a theme is presented and then varied in a sequence of sections. Each variation keeps a recognisable element of the theme, usually its harmony, bass line or overall structure, while changing the melody, rhythm, texture, key, mode or tempo. Chaconne and passacaglia are variation forms built over a repeated bass pattern. Bach's Goldberg Variations are built on an aria, and the aria's bass recurs beneath the thirty variations that follow it. Mozart's variations on 'Ah, vous dirai-je, Maman' take a simple tune and vary it in a series of contrasting styles, each keeping the tune's basic structure.

Related terms

• OstinatoA short pattern repeated persistently, often in the bass, which gives a stable frame over which other material changes.
• MotifA short melodic, rhythmic or harmonic idea that recurs and develops across a piece, serving as its basic thematic unit.
• Binary formA two-part form, AB or AABB, in which each part is usually repeated and the first part moves from the tonic toward the dominant.
• Ternary formA three-part ABA form in which a contrasting middle section is framed by a return of the opening material, usually in the tonic.

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