Multi track recording is pretty straightforward on these arrangers, as is shown here, but the tutorial is a bit dated showing an instrument with the old non touch screen and buttons, which have been gone for some time on most models from psr to clavinova.
One criticism of these keyboards - and it applies to the whole range , not just Clavinovas, is that despite providing pretty sophisticated multi track recording there is no way to do a final mix. I have done many multi track recordings on these arrangers, and no matter how good you are, there is always a need to do a final mix where volumes across every section can be adjusted in real time to get the best overall blend. A major shortcoming which has never been addressed.
Mike