For 10 points, name this work for harpsichord consisting of an aria and 30 variations by Johann Sebastian Bach.
One piece in this work is written in two time signatures, ¾ for the chords and 18/16 for the sixteenth notes, until the last five measures. One of the longer pieces in it was described as "the black pearl" by Wanda Landowska, the first person to record this piece on its intended instrument. The folksong "Cabbages and beets drove me away" is used in its ending quodlibet, a piece which deviates from this work's organization. Opening and closing with a sarabande in 32 measures, it contains nine individual (*) canons, which are collectively arranged in an ascending pattern and are located three pieces apart from each other. This work was supposedly written to cure the insomnia of Count Kaiserling, who was lulled to sleep by the titular musician. For 10 points, name this work for harpsichord consisting of an aria and 30 variations by Johann Sebastian Bach.
One piece in this work is written in two time signatures, ¾ for the chords and 18/16 for the sixteenth notes, until the last five measures.
Goldberg Variations