Air and variations
The term "air and variations" (or theme and variations) refers to a musical form. The air and variations style is one of the oldest forms of European instrumental music. The form in itself has been popular since around the 16th century and has been used by many great composers.
The air and variation style of composition lies in the principle of repetition. A theme is stated, then repeated a number of time, each time in a new guise. The composer creates a melody or rhythmic structure (known as a theme) and repeats this idea many times over. During the repeat measures, the composer will slightly modify each section to add a little variation and alter the mood. Some variations may include a change in key tonality, diminuate/augmentate or a change in tempo or feel. Up to the end of the 18th century the way in which variations were composed was usually fairly straightforward, so that it is easy to recognise the original theme behind the variation. Throughout the present contemporary period, composers have frequently made their variations far more elaborate, sometimes disregarding the original tune and perhaps only focusing on one aspect.
The theme and variation form may be classified into two groups: sectional variations and continuous variations. Sectional variations are those based on a theme that consists of one or more periods of music, each period clearly divided by a double bar line or caesura. Continuous variations are those based on a theme comprising only a phrase or two, whereby variations are introduced without interruptions such as rests, pauses, etc.
A notable air and variations work is Johann Christian Bach's arrangement of the British National Anthem, God Save the Queen. Johannes Brahms wrote many of them, to tunes by Handel, Paganini, Robert Schumann, himself, Hungarian folksong, St. Anthony chorale and so on.