- Protestant Parish Altenberg
- Gospel Choir Altenberg
- Trombone Choir Altenberg
- Domkantorei Altenberg
- Oratorienchor Köln
- Kleiner Chor Köln
- Roman Catholic Parish Altenberg
- Organ Encyclopedia by Matthias Gally (Switzerland)
- Orgelbau Klais, Bonn
- Society of the Friends of the Organ (Germany)