Theme & Variations

A simple explanation of this form is that it states a musical idea & then repeats it, varying it in such a way that it sounds at once familiar & new. If a number of such variations are put together, voila, there you have a theme & variations form. (Daniel Politoske's "Music.")

The most familiar example is Mozart's Variations on the theme "Ah, vous dirai-je Maman" (or Twinkle, Twinkle, Little Star."). A more complex & rewarding example is Dohnanyi's "Variations on a nursery tune" for Piano & Orchestra.

Bach's famous "Goldberg" variations for harpsichord are dedicated to his pupil, Goldberg, who was employed by a Count, who suffered supposedly from insomnia & wanted soporific music. The result was an aria & 30 variations.

The music publisher Diabelli submitted a waltz to 51 composers, requesting them to contribute a variation each for publication. Beethoven, in a fit of creativity, himself composed 33 variations, called "Diabelli Variations", which has become one of the most famous pieces in the piano repertoire.

Richard Strauss's symphonic tone poem, "Don Quixote" is cast in the form of an introduction, 10 variations & finale. The ill-fated knight is depicted by a solo cello, his battle with a flock of sheep depicted with most realistic bleating!

To recapitulate, there can be 4 types of variation:

1. Melody, harmony & structure retained.
2. Harmony & structure retained 
3. Structure retained.
4. Motives retained.

(From Harvard Dictionary of Music)

It can be noticed that in the last 3, the melody is not retained. Aficionados of Hindustani Classical Music may be quick to notice the similarity with the Raga Malika finale of concerts, where Ragas are changed with lightning rapidity, keeping the tala constant!