The Goldberg Variations, BWV 988, is a work written for harpsichord by Johann Sebastian Bach, consisting of an aria and a set of 30 variations. First published in 1741, the work is considered to be one of the most important examples of variation form. The Variations are named after Johann Gottlieb Goldberg, who may have been the first performer.  (source)

(via https://www.youtube.com/watch?v=BGYrk0b3Qzk)