From the OriginalHammondLeslieFaq:
When developing the PRO-3, ?JohnFisher measured his Leslie147. He found that the top rotor had a rotation speed of 400 RPM on tremolo and 48 RPM on chorale. This was with the belt in the middle pulley position and with a normal belt tension. The lower drum rotated at about 342 RPM on tremolo and 40 RPM on chorale.
SalAzz reports the upper rotor speed (middle pulley) to be 409 rpm, and lower rotor speed to be 396 rpm. Chorale speed is 48-49 rpm, for both upper and lower rotors.
DanDillon states the obvious for those who are stuck with digital simulacrums of the real thing and can't do the math for themselves: the "chorale" speed is about .8 Hz, and the "tremolo" or "lush tibia" speed is 5.7 to 6.8Hz.
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