Well since there have been no nibbles on this one, I'll go ahead and provide the answer. The work is the Prelude in C major from the WTC vol 1. This work was made famous by Gounod, who used it in an erroneous version edited by Czerny as the accompaniment for his famous and lovely "Ave Maria." In chronological order, the manuscript shows that the bass note for measure 23 is Ab, not G, and can be seen athttp://petrucci.mus.auth.gr/imglnks/usi ... WV_846.pdf
Then came the Czerny Edition of the WTC, which inserts a new measure 23 with bass note of G, advancing the original measure to bar 24. This can be seen at http://126.96.36.199/files/imglnks/usi ... e_fug1.pdf
He should still get credit for providing a new edition!
Then the first scholarly
edition of the Bach-Gesellschaft Ausgabe (BGA), Edited by Franz Kroll and published by Breitkopf & Härtel in 1866. This corrects the error and can be seen athttp://imslp.info/files/imglnks/usimg/9 ... WV0846.pdf
There you have it. The Neue Bach-Ausgabe and the G. Henle Verlag urtext edition of course have it correct, like the BGA.
If you ever accompany a singer peforming this in C major, make sure you aren't using a "proper" edition of this score, or you'll have a train-wreck at bar 23!
I think I'll take a little break from the questions now.