Hi Alan,
In "Function > Menu 1 > Style Setting > Synchro Stop Window" you can set the "Sync Stop" function so that the style playback is only interrupted when you hit a chord very briefly with your left hand. This means that if you hit the chords for a longer time than the set value, the style will continue to play normally, even if you take your hand off the keys again (despite the Sync Stop being switched on). Also see the attached screenshot.
Closing the Style Setting display with the EXIT button saves the setting in the System Setup. And of course the Synchro Stop setting is also memorized in Registrations if the "Style" checkbox is ticked.
Quote from S970 Reference Manual, page 27:
SYNCHRO STOP WINDOW
This determines how long you can hold a chord before the Synchro Stop
function is automatically cancelled. When the [SYNC STOP] button is
turned on and this is set to a value other than “OFF,” this automatically
cancels the Synchro Stop function if you hold a chord for longer than the
time set here. This conveniently resets Style playback control to normal,
letting you release the keys and still have the Style play. In other words, if
you release the keys sooner than the time set here, the Synchro Stop func-
tion works.
Hope this helps!
Best regards,
Chris