This piece is a fragment composed ca. 1780. Günther Firlinger (*1951) made a wonderful completion.
This piece is in
"Orgelbuch-Mozart-Haydn"
Carus-Verlag 2.118
The registration is only the tremmed Bordun 8 from the RP. In the middle (tenor) it sounds a bit more dry than the same stop without Tremulant, but I didn't change any adjustments. With the tremulant it's more live :-)