On Ketron, it works as such ...

SYNC START ON, SYNC STOP OFF:- Play a chord in Arranger section and arranger plays. Release chord to play another, arranger continues playing previous chord until next chord is read/detected. This is your standard operation mode. If you stop playing a style and go to select another, SYNC START stays ON (unless you manually turn off).

SYNC START OFF, SYNC STOP ON:-
Play a chord in Arranger section (and hold down for > 500ms or pre-set time in menu) and arranger plays. Release chord to play another, arranger continues playing previous chord until next chord is read/detected. Play a chord in Arranger section and release BEFORE 500ms (or preset time), Arranger goes off instantly when chord is released! Great for adding start stop effects instantly without pressing buttons or catch up with irregular timings or ... In some models, you can program CRASH to sound when arranger goes off .. great e.g for Gospel music!

SYNC START ON, SYNC STOP ON:-
Play a chord in Arranger section and arranger plays. Release chord and Arranger stops immediately. In some modules you can program so that a CRASH sound is heard when released. Great to add realistic effects/drum rolls e.g when ending a song.

SYNC START OFF, SYNC STOP OFF:-
Drums only are heard when Arranger is played. No chords nor bass.

Ofcourse you can program different settings into different song memories/registrations.

Thanks,

AJ