BWV 570 - Fantasia in C Major Uploaded by: DavidJ Composer: Bach, J. S. Organ: 2012 Kamiński, St. Anne's, Długa Kościelna Software: Hauptwerk VI Views: 70
Well, most common of cause is the use of a Vox Humana or so, imitating an Italian tenor.
On the organ of Riddagshausen however I prefer this very soft registration, it sounds better in my opinion - let's say it's now a countertenor :-)