Hi Guys,
PA3X / PA800 makes for a great controller for a sound module.
In Style Play Mode
press Menu Button
press Track controls
Press Track select button to toggle between Accomp Tracks & Lower /Upper Voices.

Default is BOTH for each of the tracks , but you can also set to internal or external. Press External to use a sound module, & at the top set the Bank & program changes required for the external voice you want to use.
When finished, drop down menu & write it to a STS so it's permanently linked to that style.

Off topic , but
I used to use this method for playing the drum & percussion tracks for my ketron style conversions. PA800 sounds were great for bass, piano etc, but PA800 couldn't play those ketron Live drum tracks , so I used the sd2 instead for the Live drum & Drum tracks.