Hi Al...yes, I have some of the same frustrations with SA organs, although, I must say, I do love the sounds a lot (especially ProgRockOrgan!).
For Organ Flutes, I use a foot-switch for Rotary Speed change...mainly because it affects all organ flutes I have on, as in Right Hand (including layers) and also the left hand sound. It's also a lot easier than using a panel switch or a wheel.
For the SA organ Rotary Speed change that is assigned to the mod wheel, I assign it to a pedal switch...Direct Access, step on the pedal I want to assign, and use "C" and "D" buttons to pick what I want it to do...
MODULATION gives fast rotary when the pedal is pressed and held down.
MODULATION(ALT) changes the speed each time you press the switch and it stays that way until you press again.
I wasn't aware you could assign the mod wheel to Leslie slow/fast on the Tyros2's custom voices, as I never tried it....you say the method is removed on the Tyros4?
Ian
PS...I sent you a PM.
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.