Geist's third choral prelude is based on the melody of "Allenaste Gut i himmelrik", in other parts of the world known as "Allein Gott in der Höh sei Ehr".
It is very different from the other two. It does not feature the chorale melody as an elaborated solo voice. It is more like a hymn setting, in which part of the choral melody is played with the pedals.
The chorale melody has the so called Bar-form: the first part of the elody is repeated, after which follows a first part. Schematically this form is represented as A-A-B. The first A is played with the pedals as bass voice, the second A and the B are palyed with the right hand as soprano voice.
It is a solidly written composition, based on a solid chorale melody. The registyration in my performance is therefore an equally soli principal chorus, in the last bar even joined with the Prestant 32 in the pedals. Though you need good headphones to really hear it.