Connecting to the Leslie 2101 mk2* - 8Pin Cable
(* the following applies only to the 2101 mk2; the original mk1 does not accept "stationary" L/R audio thru the 8-pin connector.)
The pinouts on the SK's 8Pin connector are:
1 - Rotary audio out
2 - Leslie detection ("sensing" ground indicates the presence of an external Leslie)
3 - audio ground
4 - Stationary L audio out
5 - ground
6 - Stationary R audio out
7 - speed Fast toggle
8 - speed Stop toggle
If you want to build your own cable for the 2101, you must cross-wire pins 4-1-6 to 5-3-7 since DIN cables use male connectors on both ends. This gives you a "mirrored" cable that is agnostic to the connectors -- in other words, it won't matter which end you plug into what:
1 - 3
2 - 2
3 - 1
4 - 5
5 - 4
6 - 7
7 - 6
8 - 8
2 2
<-- 4 5 <-- --> 4 5 -->
<- 1 3 <- -> 1 3 ->
8 8
<--- 6 7 <--- ---> 6 7 --->
With this cable (or Hammond's identically-wired LC8-7M cable) in place, the SK will deliver three channels of audio (mono organ, stereo "extra voices") and speed-control (stop toggle, fast toggle) to the Leslie 2101 mk2.
Making a "Breakout" Cable
If you don't have a Leslie 2101 mk2, but still want to externalize the 3-channel audio and speed controls, you'll need to build a cable that goes to ground on Pin 2. If the SK "feels" ground on that pin, it assumes an external Leslie is present, and routes the audio and speed control signals to the other pins on the connector.
I have not built such a cable myself, and am probably not sufficiently qualified to do so. I invite the more "electrically gifted" to post complete (and safe) instructions in this space...
Configuring the SK to use the Leslie 2101 mk2
Refer to pages 84-86 in the SK "Owner's Manual", and set the "Ext.Leslie" setting to a value of "3"; this selects a 3-channel Leslie (i.e. the 2101 mk2)
The "Bypass" Switch
Just as with the onboard Leslie sim, your normal playing position is with the Bypass switch OFF. In this mode, the 8Pin connector sends all three audio signals (organ, EV L/R) and the two speed toggles (stop, fast) to the 2101.
If you turn Bypass ON, Pin 1 is muted, and the "rotary" audio is rerouted to the "stationary" audio on Pins 4/6. In this mode, the 8Pin connector sends only L/R stereo audio -- the organ and EVs are submixed together, exactly as if you were using only the dedicated L/R 1/4" outs. The speed controls are still active, but useless since no rotary signal is present.
(Except for the "breakout" cable, I've tested and verified everything above on my own gear. Thanks to JMcS, B3-er, and Eryk at Hammond-Suzuki for helping me to sort all this out! )