This might get a little confusing so I'm sorry if you have trouble understanding what I'm trying to explain.

Ok, just the other day (Sunday to be precise), our choir sang on a Sunday afternoon on a barge on the river. We had live music. We had a Roland FP-9 for the piano and the organ (to my suprise) was an Alesis QS7. I had heard that the QS series had an organ sound,like all other keyboards you'll find, but what I didn't know is it had a rotary speaker simulator and a leslie effect on it to make this organ sound like a real organ with a tremolo switch on it.

What I would like to know is what effect makes this organ sound like a real organ w/ a tremolo switch. Is it the rotary speaker simulator or the leslie effect?

I am looking at buying an Alesis NanoPiano and it has a rotary effect for the organ sounds, is this what I'm looking for where I can switch it on and off like I would if I were playing an organ with a tremolo switch. Or would I need the leslie effect.

I hope you understand what I"m trying to explain, it may sound confusing to some, I just hope I can get an answer. I don't want to buy something if it's not what I want.