Bach's autograph is lost, but the piece is known through the copy (P 595) made by J. F. Agricola, who began his study with Bach on that year.
Many variants are concentrated on bb.15 ff 
.
Bach's autograph is lost, but the piece is known through the copy (P 595) made by J. F. Agricola, who began his study with Bach on that year.
Many variants are concentrated on bb.15 ff .
No autograph survives. The 'London autograph' is a copy made by Anna
Magdalena. This version is the ante correcturam version. .
Sometime after WTC II was complete, Bach revised the soprano in
bb.13-14. This revision is reflected in both autograph collections .