Hi Tony.
Mystery Solved!
Rico used Yamaha's: "Registration Memory Sequence" feature,
enabling him to automatically trigger "pre-programmed" Reg changes with his right foot via foot switch pedal.
If you look very carefully, the footswitch cable can be spotted leading out from his right shoe.
A split second right before he switches from the organ sound to the guitar sound on Tyros 4
you can see him quickly and discreetly activate the foot pedal @ approx 1:34 and then press it again right before he returns to the organ sound. The Registration button lights change accordingly from reg 2 to 3 and back to 2 as well.
Recalling the many heated Synthzone debates over the years here
about playing along to midi files vs auto accompaniment style playing,
I think Rico's skilled talent at playing along to "midi backing tracks" impressively showcases
the benefits of playing along to a midi backing track vs limiting arranger keyboard playing to auto accomp style playing alone.
Rico, that's very impressive footwork on your part, esp on such a quickly moving song.
You even had "me" fooled there for a bit.