The sounds produced by the Leslie Cabinet are very complex in nature. Basically, the cabinets contain a rotary twin horn, acoustically coupled to the treble loudspeaker and a rotary drum shaped baffle coupled to the Mid range/Bass loudspeaker.
These rotary elements are driven by electric motors capable of two different speeds - commonly named as Chorale (Slow) and Tremelo (Fast).
The resulting sound is a combination of both amplitude and frequency modulation, caused in part by the Doppler effect, and is a rich and complex mix of tremolo, phasing, pitch-shifting and ambience.
A further complication is the effect intoduced as the speed of 'modulation' is changed from Chorale to Tremelo and vice versa, as the motor speeds accelerate and decelerate. This effect can be clearly heard in the recording of 'Whiter Shade of Pale' by Procol Harem.
It is difficult to reproduce these effects realistically by purely electronic means since much of the effect produced by the Cabinets, is purely 'acoustic' in nature. However, there are electronic devices available which can produce close approximations to the 'Leslie Sound' - usually called 'Rotary Speaker Pedals'. They would connect to the line outputs of a keyboard and then to an external amplifier/speaker combination. However, none of these devices which I've heard, can produce the rich, spacial sound produced by a Real 'Leslie Cabinet'. They get 'near', but........
Regarding reproducing the 'Leslie Sound' on the KN7000, I've spent many hours experimenting within the available sound effects, but have never achieved anything really close to that unique 'Leslie Sound' effect.
So Rog, perhaps you are looking for 'The Golden Fleece' ???
After silence, that which comes nearest to expressing the inexpressible is Music.