Those studying composing/arranging and listening in SQA Music exams pretty soon come upon variation form. If you’re lucky enough to have an iPhone or iPad you can download a free app containing a recording by Kimiko Ishizaka along with a score (with moving cursor) of one of the best sets of variations of all time, Bach’s Goldberg Variations.

You can get the iPhone app here  http://www.opengoldbergvariations.org/soundsnips-free-iphone-app-featuring-open-goldberg-variations

and the iPad version here:

http://www.opengoldbergvariations.org/musescore-releases-free-ipad-app-open-goldberg-variations