Ah, the French Organ Movement.
Franck has to stand next to Bach in his organ music. It far outranks his symphony, tone poems and (maybe) the Violin Sonata in A.
His Grand Symphonic Piece in F# minor is a masterpiece and shows just how effective he was as a composer for organ. The pedal work in the finale is mindboggling.
The Fantasie in A is not something you want to hear in a dark room. He spins a 4 bar unit out to heavenly length but spends very little time in A Major, using 3 sharps as a key of convenience while he travels elsewhere. And it's a very spooky trip, ending in A minor.
There are rumors in the air of a new organ . . . maybe when it's installed (if we're all still alive then). The current organ is not that great, certainly not worthy of the beautiful room, which has perfect acoustics for chant and polyphony and also for organ.