Theme and Variations
A Theme and Variations is a theme, followed by any number of variations, which are different arrangements
of the initial theme. Most commonly, the melody line is varied, by adding extra
notes around the theme, perhaps in a semi-quaver pattern when the original was in crotchets or quavers.
In the Early Music and
periods, the theme may stay constant for one voice part throughout, while the
other parts perform the variations. This was called cantus firmus.
In the Baroque period, the bass line
may remain constant while the top parts weave around in harmony with it. This
was called a ground bass. Also in the Baroque, the harmonic
sequence may remain constant, while the top line varies, but always in
harmony. (There is some similarity between this and
or Dixieland Jazz).
In the classical and
romantic periods, variations
were usually on the melodic line itself. These may be faster decorations weaving
around the tune, or a paraphrase of the tune, or a change between major and
minor keys, and so on.