How to create this effect ?

Sounds like Tremolo ........ ?

Cheers !

Try putting the Rotating Speaker after the amp stack (X, MOD,Delay, or Reverb slot).

Or, try my “Touch Speed Rotary 2” rig from The Rig Exchange. You’ll likely want to set the speed to fast.

it's all in the 'tache.

Chu made a mustache joke.

That video is an excellent example of showing how he uses the volume knob, and changes the guitar position to get long sustain. There is even a point in the video where the note stops sustaining, and he changes volume and position to regain it.

Quote from Algado

Ha ha... My question was : Europa in 1976. Your explanation is not useful for the question :)'

In 1976 I played that part thru the a real Lesslie, join to an Hammon on stage , today, Kemper numeric Lesslie is not credible...

But I heard some guitar player using tremolo...

My first response to your question offered some programming suggestions, and a rig to use as a starting point. My second response was to your second question, and I added an additional comment about the video you provided.

The Kemper Rotating Speaker sounds much fuller in stereo than in mono. But, if you want to fully recreate your experience from 1976, you'll likely need to get a 122 or 147.

Quote from Algado

Yes, unfortunatly.... Original Hammon Leslie Cab was not in stereo.
They should add more "volume variations"

are you saying that you don’t want the Kemper rotary effect to be mono like the original Leslie? If so still put it after the Stack section but set the stereo parameter to 0.