About Johann Sebastian Bach's Small Preludes and Fughettas
Collections of short keyboard preludes by Johann Sebastian Bach have been around since the 18th century. For instance, the Six Preludes, BWV 933–938 were probably arranged by Bach himself in systematic order according to key and difficulty.
The Twelve Little Preludes were a 19th-century compilation extracted from two manuscripts, the Klavierbüchlein für Wilhelm Friedemann Bach, and the Kellner Collection of the Berlin State Library, both with dozens of works by various composers and written down by multiple known and unknown scribes. In the 20th century, Ferruccio Busoni combined the Twelve Little Preludes with the Six Little Preludes, BWV 933–938 into a set of 18.
The probable date of origin of most of these pieces is around the first half of the 1720s, that is the period of Bach's later years in Köthen and his first years as Thomaskantor in Leipzig.
The little fugues and the preludes with fughettas take the player a step further; they were used in Bach's circle as preparation for the more difficult works of the Well-Tempered Clavier.