The Grand Pièce Symphonique is often considered to be the work that set the tone for the French Organ Symphony: written in 1860-62 it is dedicated to Charles Valentin Alkan - a composer whom Franck admired and who had previously written both a symphony and concerto for solo piano. It features three continuous movements, and themes which are connected and developed throughout.
Franck said, "Mon orgue, c'est un orchestre" and this work must have been astonishing in its day.
I recently participated in a three-concert, four organist, Franck marathon and this wonderful work was one of my assigned pieces. I hate to admit that I was not very familiar with it before (perhaps the duration alone is a barrier to entry) - but after studying it these past few months, I have really grown to love it.
This performance is not perfect, but captures the essence of how this piece speaks to me: I look forward to becoming more secure with it in the years ahead and will look for opportunities to share it in public again!
I highly recommend finding 25 minutes, good headphones/speakers, a comfy chair, and enjoying Franck + Cavaillé-Coll
Score:
https://imslp.org/wiki/Special:ReverseLookup/3781
PS: Here is a playlist of our Franck Concert Series from Second Presbyterian Church, in Portsmouth, Ohio.
https://youtube.com/playlist?list=PLp6Uk_yLNQaDpgTEzB247hieXWGXnBl83