This piece is usually called the “Big e-moll” to distinguish it from its smaller brother, BWV 533.
It presumably originated in Leipzig between 1723 and 1729.
Together with the Praeludium und Fuge in Es-Dur (BWV 552), the H-Moll (544-1) and the C-Moll (BWV 546) it belongs at the summit of what Bach wrote for the organ.
It is also one of his biggest pieces: in my edition a full 14 pages.
There is a copy of this piece written by Bach himself in “Reinschrift” (best corrected version), consisting of the Praeludium and 20 bars of the fugue, which originates from between 1727 and 1731.
There are eight older autographs from which the rest of the fugue could be constructed.
There is a great consistency thematically between the praeludium and the fugue.
Both are written in A-B-A form. The use of scales and scale like motifs in the harmony bind the two parts together.
Spitta marveled at the life energy and the daring of the fugue subject and called it “a two part symphony”.
Altogether a wondrous work: for those interested and able to read German, here is a link:
I played this monument in a competition many, many years ago and had not touched it since, so I wondered if I still could play it. It took me about a month to relearn it; it had faded away almost completely.
It was truly marvelous to re-discover the wonders of this masterwork.
It IS a bit of a sit-in and you have to take your time to listen to it (and perhaps also getting to love it) but it is worth it.
I sincerely hope you like it.