Hi JayR, long time no talk ! )))
Hammond organ representation on computer based samplers like Hauptwerk, GrandOrgue and jOrgan is difficult. In jOrgan community we have some examples which are pretty cool but IMVHO are far from perfect. In VSTi world we have some very very good and close to original representations :
1. The now classic and out of production B4, B4II from Native instruments (no samples)
2. The superb VB3 created with physical modeling (no samples too) where there is a Leslie VST named McDonald too.
3. The standard Vintage Organs Library for Kontakt 5 from Native Instruments containing samples from B-3, C-3 and M-100, which is IMVHO the best of them all.
To represent accurately a Hammond one needs samples from the tone wheels with all imperfections and/or leaks and then on sampler to use volume sliders to represent the drawbar action. Also samples from percussion and key click.
The leslie thing is the hardest, so one has to sample again the same as above with Leslie on , in both slow and fast speed. Then use the alt attack function in GrandOrgue for example, to get it, as we do with the pipe organ temulant samples.
Even like this though we cannot get the real leslie close to original because we will not have the speed rate changes and many more stuff, like the moving speakers noise.
That's why even modern times Hammond company has built in a simulated leslie function more or less like a computer VST effect.
Another easy way to get a Hammond into GO is to use straight samples of the tonewheels, engage them with a swell pedal each (using a different image on GUI) , ie 9 in number (16', 5'1/2, 8', 4', 2'2/3, 2', 1'3/5, 1'1/2, 1'), create 9 stops default to engaged and 9 windchests each with its own enclosure referenced from each stop, then use Jack to mix the output of GrandOrgue with the McDonald Leslie sim VST (free), or have slow leslie samples as the straight ones and use the alt attack function for the fast leslie samples by engaging the tremulant switch on GUI. This will give a modest and high quality Hammond organ representation.
Concluding, IMVHO, NI vintage organs library is the best nowadays representation of Hammond organs for computer based organ setup.