A rather heavy "Fantasie über die erste Choralzeile von 'Komm, heiliger Geist, Herr Gott' by Selmar Müller. Highly romantic and that's why I chose for my virtual very spacious 'Caen 4-Manual Extension Cathedral' again :-)
The only thing I can find about the composer Selmar Müller is that he was a music director at a seminar and organist at Wolfenbüttel (North Gemany).
It's a Maestoso composition, straight forward, but I took some liberty (tempo, rests, registration) to fit my performance in the challanging acoustics.
The theme of the chorale is not used in a very strict way (I didn't recognize it immediately), but is heard at several places and in the end in the pedal (stretched over long notes).
A lot of dynamics and echoes.
The way I like to play and listen this piece/recording is imagining that I pass by a huge cathedral, have a seat and let all the sounds, the space and atmosphere come over me ... drifting on the sonority of the organ sound and those amazing acoustics ...