Although written for Clavier or Piano, Bach's fugues can readily be arranged for different instrumental groups. Fugue No. 24 from Book 1 (of "the 48") is in four parts, and easily arranged for String Quartet. Here is a printable PDF version of the Score and each of the instrument parts for Violin 1, Violin 2, Viola and Cello. Here is the original version of the fugue for reference, and here is its corresponding Prelude in the same key of B minor. The complete collection of Bach's 48 Preludes and Fugues are available as follows: Book 1 and Book 2 from Sheet Music Plus.