The Bach Busters series 'unlocks' some of the less well known but equally beautiful Preludes and Fugues from J. S. Bach's Well Tempered Clavier, through transposition and subtle re-notation.
Fugue III in C (original C#)
Fugue VIII in D Minor (original D#)
Fugue XIII in F Major (original F#)
Fugue XXIII in C Major (original B)