Bill,
I think you are much closer to the mark in your reply.
I tried it on my PR903 pianner, and all sounds marked with DE had the Digital Effect light on, and the fast Leslie/Tremolo/Rotary speaker sound.
Those with NE (No Effect), had no Leslie/Tremolo/Rotary sound.
The Organ Bass marked DE had no Digital Effect light on, and no Leslie sound, but when the DE button was activated it had a slow Leslie sound. Slight oversight (as architects like to say) by Technics maybe, but no big deal. My vote is Digital Effect, and No Effect.
Ray

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Ray The Saint