Sigfrid Karg-Elert (born Oberndorf am Neckar, 21 Nov 1877; died Leipzig, 9 April 1933)
Number 15 of Opus 65 Herzlich lieb hab dich, o Herr
The music is here;
http://ks.imslp.info/files/imglnks/usimg/3/3f/IMSLP225797-SIBLEY1802.17229.632b-39087012466936vol._2.pdf
66 organ pieces composed between 1906 and 1908. They were first published in 1909 and dedicated to Alexandre Guilmant. Op 65 includes the well known Nun danket alle Gott.
Karg-Elert was a German composer and teacher whose most notable influences included Carl Reinecke, Edvard Grieg, Claude Debussy, Arnold Schoenberg, and Alexander Scriabin.
His favourite instrument to compose for was the Kunstharmonium, a versatile French creation that allowed him the range of colors he preferred. From 1924 he gave weekly radio harmonium recitals from his house. To see Karg-Elert's creativity and the flexibility and range of colours offered by the Kunstharmonium have a look at Opus 101. Musical portaits of 33 composers from Palestrina to Schönberg.
I have used the Riddagshausen organ that I really like and I think it handles this music quite well. This sample seems to have slipped down the list a bit now that there are so many other organs to choose from.