Mozart’s Variations in C Major provides an easy example of the concept of theme and variations. He takes a simple melody in 2/4 time and creates 12 new versions of it.
In the first variation, the tune is placed on the second and fourth places in groups of sixteenth notes, which is not where the ear would normally hear it. Mozart plays with this variation by making the left hand soar through the phrase and then hint at a bass line as it progresses to the resolution. The second variation has sixteenth notes in the left hand while the right hand is playing an exquisite series of suspensions that eventually resolve at the end of this section.
The third variation dances around the melody by using triplets in the right hand. Trills appear in the right hand, and the notation is divided between slurred notes and staccato notes to give emphasis in certain spots. The fourth variation puts the triplets in the left hand while the right hand reiterates the melodic suspensions set forth in the second variation.
The fifth variation springs into a completely different feeling, as both hands take on an impudent and syncopated presentation. Here the listener can find phrases where Mozart has notes in the left hand sustained as the right hand plays the melody, as well as sustained notes in the right hand while the left hand is moving through its part. The sixth variation pairs a detached melody against chromatic sixteenth notes, with the movement crossing between hands. The seventh section uses scales in the right hand and sets of three sixteenth notes to offset the solid bass line in the left hand.
For the eighth variation, Mozart changes the key signature to C minor. Here the arrangement of the melody in the right hand is echoed in the left hand. The ninth variation, which returns to C major, turns the echo of the previous section into a true fugue as four voices take up the melody. The tenth variation features quarter notes played by the left hand accompanied by a sixteenth rest and three sixteenth notes in the right hand. The left hand jumps across the keyboard to switch between the melody and the bass line.
Mozart includes the word “adagio” at the beginning of the eleventh section, which includes some fugal voicing, syncopation, ornaments, and triplets. For the twelfth and final variation, he changes its time signature to 3/4, marks it “allegro,” and uses trills and sixteenth notes to move the listener toward a satisfying conclusion.