Here is my simple take on the Leslie Rotary Speaker.
This patch is very simple, no reverb, just the rotary simulation.
The sound is going though a SV-Filter, sending bass under 200Hz to the output.
Then the remaining frequency is splitted at 800Hz.
-Lower mid goes in a pitch shifter, very very slight as the doppler effect is less pronounced on bass frequency in a Leslie cabinet. Then in a panner.
This side is controlled by a LFO, 40rpm for slow speed, 340rpm for fast speed as a real Leslie.
-Upper freq goes to another pitch shifter, more pronounced and then in a panner.
This side is controlled by another LFO going from 50rpm to 400rpm.
-Left switch press switch from low speed to fast speed. Ramp is slower for the bass rotor as in real life.
-You can control also the speed slow to fast with a Midi CC (I do so with my Es-8).
I took informations on those pages: