Ca. 2 weeks ago Agnus_Dei posted this fine set of variations and attached the score.
Here is the link to Davids fine upload played on the Salisbury-Willis-Organ:
https://www.contrebombarde.com/concerthall/music/45958
In Davids description you'll find many informations about the composer and the piece.
I was VERY excited by this fine music, so that I made an own recording with a complete different Organ: The Bätz-Organ from Utrecht, where I found some nice registrations for this.
The theme is a duet from the "Magic Flute" by Mozart "Bei Männern, welche Liebe fühlen..." (La Dove Prende)
Please enjoy to compare two very different recordings!