I think it's about time I posted this, as it's been sitting around here for some time, and sees quite a bit of use.
[Updated 3 Dec 2008 -- see end of full posting.]
A year or so back, I was getting all frustrated because I couldn't find anything that I could play from keyboard that really sounded like the Hammond organs I was hearing on record. The one on my new digital piano was particularly awful. Then I came across Hans Mikelson's "Rotor Organ" here, and a lot of my frustration disappeared.
However, I still wasn't quite satisfied [am I ever...? (:-/)] and have been tweaking it ever since. I think it's now quite a creditable replica of the various moods of the Hammond, so is worth republishing. It is intended strictly for live performance, with midi inputs for two manuals (no pedalboard). Drawbars and Leslie speed can also be controlled through midi, if you have suitable channels -- or by score commands on stdin if you don't.
It has a fairly exact emulation of the Hammond Vibrato, which was missing from Hans' version, and it even goes as far as using the Hammond's precise tonewheel frequencies (derived from number of teeth and shaft gearing) rather than Csound's built-in equal temperament values.
I've made it available as an archive (tgz or zip) as well as the CSD source now attached here, because the package does have an additional README and some presets (as i-commands). There are some more details on a web page, and if you want to delve into the technicalities, there are some more details here.
Apparently it's not possible to upload tar or zip archives (dangerous, maybe?), so I can't post the full archives above.
So to get all the details just grab them at the above web page.
I've now (3 Dec 2008) updated the organ code a bit more. The output volume is now better balanced over the note range, has a reasonable 'key-click', and is compatible with Csound 5. (It turned out that some usage of Csound 4 doesn't work in 5.)