I found this jam session on the net...comparing the Yamaha P-85 to Casio PRIVIA PX-320:

Yamaha P-85 and Casio Privia PX-320 in action

I believe the rhythm comes from the PX-320 and the keyboardists alternate in using the piano sound and electric piano patches.

PX-5S FA-06 LaunchKey 61 SL-MKII Graphite 49; VST: Pianoteq 6+Bluethner UVI TrueKeys EWQL-SO + Hollywood Strings/Brass, AAS GS-2+LL EP4 Sonokinetic; Mobile DAW ROG G751J: i7 4720 32GB RAM 250+500 GB SSD Scarlett 6i6 TS110A x2; https://www.youtube.com/channel/UCfiQst_xQwNgKL_FS9OXSKw