I am an amateur organist & love nothing (except reading) as much as I love the organ. This piece is my favorite. The next to last section, just before the pedal cadenza, makes my heart race with joy. I love the whole piece, but that particular section, Wow! It's to swoon for!
Actually, I agree with you. It looks intimidating to learn when watching someone perform it. But once you see the score you see that it really is not too too bad. It just requires good technical skills, especially in the pedaling.
I don't believe this is as hard as the previous two commenters have said-it often has imitation as they said, but it has a predictable pattern and the fingering is not very diifcult to figure out.
The Preulde and Fugue in D Major of Bach seems to be a piece of constant immitation. It seems as though Bach said to himself "I will write a piece that will show that the feet can do exactly what the hands do and vice versa." The Prelude begins with a very brilliant pedal scale or run up the keyboard. The Fugue, which again seems to be constant immitation ends with a pedal solo or cadenza.
En fait je la joue au piano, ça rend pas mal, mais c'est un peu différent de la transcription par Busonni pour le piano Bon courage et n'hésitez pas a la travailler