The Golberg Variations BWV 988 by J. S. Bach, are a good example of variations in the baroque period. It is a work of great proportions based on a theme titled Aria followed by 30 variations.
The Aria is in binary form. Each part is made of two phrases:
Here is the structure of the Aria:
This structure is followed in all variations (we will discuss minor variations later). Each section normally has 16 measures, but in some variations two measures are combined into one, so each section has only 8 measures. In variation 16 (overture), part B has 32 measures because part A is in 2/2 (the overture) and part B is in 3/8. In this case, two measures of part B, correspond to one measure in the Aria.
Some harmonic variations of the original are found. Here we compare the Aria and the first variation with variations marked in red:
|Key||G major||D major|
|Aria (theme)||I||V||vi - vii / V||V||I - V / IV||ii||V||I||I - vii / re||I||ii||V||I - V / IV||IV - ii||V||I|
|Variation 1||I||V||vi - V / V||V||I||ii||V||I||I||iii||ii||V||I||IV - ii||V||I|
Measures 17 to 32:
|Key||G major||E minor||G major|
|Aria (theme)||V||I||VI - ii||V||i||VI||ii - V||i||ii||I||ii||V||I - V / IV||IV||V||I|
|Variation 1||V||I||iv - ii||V||i||iv||V - vii/V - V||i||ii||I||ii||V||I - V / IV||IV - V - vii/ii - ii||V - I - V||I|
The G and D minor keys are used instead of the major keys. In part B, instead of E minor, Bach modulates to E flat major:
Variation 15 is a canon at the fifth using mirror inversion (the sixteenth notes motive is imitated in the second measure one fifth above and the interval direction is inverted). The two upper voices make the canon over the bass: