Hi Michael,
Here is a small addition to John's tip:
If you want to memorize the Left Voice (and its On/Off status) in a registration, but you do NOT want this registration to change the current style later, you have to use a little trick:
1. Copy a style (e.g. a preset style) to a USB stick that you use exclusively for this purpose. It is best to give this style a unique name on the stick, e.g. "dummy".
2. Load the "dummy style" from this USB stick.
3. Make the desired Left Voice settings.
4. Memorize the desired registrations and save the registration bank (with the Style box ticked).
5. Now remove the USB stick with the "dummy style" from the keyboard.
6. If you call up this registration(s) later, only the Left voice will be switched/set, but the current Style will not be changed.
By the way, if the Right voices are also to be changed/set by a Registration, the "Keyboard Harmony/Arpeggio" box should also be ticked next to the "Voice" box. This also applies if the Keyboard Harmony/Arpeggio function is currently not used at all. The reason is that this is the only way to turn "Keyboard Harmony/Arpeggio" OFF by Registration if it was previously enabled.
Best regards
Chris