Variation
A change of a theme.
What it means
Variation designates the changed repetition of a theme and at the same time a form that rests on this procedure. In a set of variations, a theme is first presented, after which a series of variations follows, each of which shows the theme in a new shape. What is preserved in the process and what changes determines the character of the form.
Musical use
Several basic types can be distinguished. In the ostinato variation, a bass figure or a harmonic frame stays unchanged, and the upper voices change with every pass; this type was widespread in the seventeenth and early eighteenth centuries. In the figural variation, melody and harmony remain recognizable in their outlines but are played around with changing figures, for instance in ever smaller note values. In the character variation, the expression changes fundamentally — tempo, time signature, mode, texture — while the connection to the theme is preserved through individual features. A frequent device here is the change to the same-named minor or major key, marked in editions as minore or maggiore.
In the nineteenth and twentieth centuries, the free variation developed, in which the theme serves only as a starting point and the changes move far away from it.
Variation is to be distinguished from motivic-thematic work: the latter breaks a theme down into motives and works them individually, the former changes the theme as a whole and mostly keeps its structure.
Variations over a constant bass include the passacaglia and the chaconne, which are to be distinguished from variations over a melody. Great cycles of the keyboard literature are Bach's Goldberg Variations (BWV 988), Beethoven's Diabelli Variations, op. 120, and Brahms's Variations on a Theme by Handel, op. 24.
Performance practice
With every variation, make clear to yourself what is preserved from the theme — melody, bass, harmony, or only the structure — and let this framework become audible. Give every variation its own character. And plan the whole cycle as an arc, rather than shaping each variation for itself.