Some "French"recommendations:

Tournemire: l'orgue mystique
a cycle of meditations on gregorian themes coloured with late romanticism,
very innovative in form (not unlike Messiaen's juxtaposition techniques)

Vierne: pieces de Fantaisie
Very powerful and highly imaginative music.  Look out for "Der Rhein".
(Another excellent recording available by Ben van Oosten; glad you liked
the symphonies).

Langlais: Meditations sur l'Apocalyps
The perfect syllabus of French 20th century organ tradition.

Franck: Chorales
Numorous fine recordings available.

greetings,
jos
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