G.A. Merkel is mostly known for his Organ Sonata no. 1 in D minor, for two organists. He composed 9 organ sonatas in total, and here is Sonata no. 7 in A minor.
The Sonata has three parts:
00:00:00 Moderato assai
00:04:28 Andante
00:09:55 Allegro risoluto - Più moderato
The registration is constrained by the fact that I play without assistant, and it is not always possible to switch combinations since hands and legs are fully occupied most of the time.