Although there exist many copies, no original manuscript of the piece remains, therefore the date of composition is unclear. But it is believed to have been completed around 1720. It was highly praised during Bach’s lifetime, and was already known throughout Europe in the 18th century. Even in the 19th century, many famous composers, including Beethoven, published revised versions, and there are records of performances held by Mendelssohn, Liszt, Brahms, and others.

This piece, which combines the composer’s rich imagination with the strict contrapuntal form of fugue, beautifully expresses the contrast between “freedom” and “discipline”. The romantic and improvisational fantasy progresses in a brilliant, galloping toccata style in the first half, and in the second half, marked as recitative (recitation), dramatic contrasts of dynamics and unexpected key changes are repeated, fusing it with toccata elements. The following fugue is in three parts based on a chromatic theme and although limited to the minor keys, it modulates to distant keys and gradually builds up tension. After a massive statement of the theme in a wide range, the piece concludes with a brief recollection of the chromatic theme used in the Fantasia.