Here are some excerpts from "Charles-Marie Widor, THE SYMPHONIES FOR ORGAN, Symphonie romane", edited by John Near:
"When one May Sunday [in 1900], still striving with technical problems, [Widor] played for the first time in St. Sulpice the Symphonie Romane, I felt with him that in this work the French art of organ playing had entered sacred art, and had experienced that death and that resurrection that every art of organ playing must experience when it wishes to create something enduring."
In these words, Albert Schweitzer expressed the almost unspeakable awe that he and countless others since have felt upon hearing Widor's last organ symphony. Truly, it represents a pinnacle in the art of organ composition. Five years earlier, in the Symphonie gothique, opus 70 (1895), Widor had sought to bring his organ art into the realm of sacred art by including plainsong in two movements. With the Symphonie romane, he turned wholeheartedly to this endeavor; sacred melody became the very fabric of the symphony's structure. What resulted is the work man yconsider to be Widor's greatest organ masterpiece.
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Widor had formed a very personal concept of organ music through years of observation and experimentation, and he had written in forms that many considered secular. With the last two symphonies, he expelled all that. Organ music became for him "a special kind of music, the music of the eternal, awakening thoughts of immortality." The romane dedicates all to the "imperishable spirit." Its composer confided that he could no longer conceive of organ music in any other terms: "It is noteworthy that...except for certain preludes and fugues of Bach, I can no longer think of any organ art as holy which is not consecrated to the church through its themes whether it be from the chorale or from the Gregorian chant."
This book also reveals that Widor first performed this symphony in Berlin, and also played Bach's Fantasie and Fugue in G minor (BWV 542) at the same recital. What a coincidence--I'm also playing that piece at my recital!