The Well-Tempered Cl. II, Vol. 6, 2 four-part Preludes and Fugas, for String quartet
after the original version for piano (harpsichord) https://music4viola.info/work-info/60/Bach%20J.s./the-well-tempered-cl-ii-vol-6-2-four-part-preludes-and-fugas-for-string-quartet