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. 
