Hello,
Since the reverb is essential for an organ to sound, I guess you might be interested in this site:
http://www.openairlib.net/auralizationdbAmong the different impulse response provided, two of them are particularly clear:
-
Lady chapel St Albans cathedral, short release time (RT60 = 2.34s), for a well defined sound
-
York Minster cathedral, long release (RT60 = 7.65s) but still a clear sound
On Debian (should work on Ubuntu as well) I'm using them with "jconvolver".
Vst are available for Windows. For instance
here.
Enjoy,
Davy