Help with Kawai ES4 Multi-timbral midi operation?

Hi all,
While thinking reading through the "Help me choose a synth" thread, and dealing with the feelings of desire to buy more gear that sort of reading entails, I suddenly thought that maybe my old digital piano (a Kawai ES4) would probably be a good tool to begin learning about the world of hardware synthesisers...
I grabbed the manual, and sure enough it has midi in/out controls (no surprise there), but it talks about a "Multi-timbral Mode" for midi operation:

Multi-timbral mode allows the ES4 to receive data on more than one MIDI channel simultaneously.
In this mode, the ES4 can play different musical parts with different sounds for each part.
Multi-Timbral On (On1 and On2)
This is a flexible 16 part multi-timbral setup. You can turn individual MIDI channels on
and off, and assign any program number to any channel in the way you like. The ES4's
normal program change numbers are assigned in On1 (Please see page 28 for a list of the
program change numbers), and General MIDI program change numbers are assigned in
On2.

This sounds like a super fun thing to do! It's got decent analog piano sounds, digital piano sounds, drum sounds, string pads etc so I wanted to try and do some composition using it as the sole sound source...

Only I can't work out how to get it to play a different sound on each midi channel!

  • I've got it happily playing back a tune with a single sound
  • I've tried both multi-timbral modes On1 and On2

But in both modes, no matter what # midichan I send the commands over, it always plays the same sound.

Pg 24 also talks about Channel Mute, and controlling the muting of the 16 channels - I've confirmed they are all unmuted

The manual can be viewed here:
https://drive.google.com/file/d/1aJfelyZkREAd2RWcRap-Wdtr9IN58UzM/view?usp=sharing

It's a long shot, but I'm very new to this stuff and am probably missing something obvious - can anyone here offer any help (even suggest a better place to ask) or have any experience specifically with the Kawai's midi operations/setup?

Thanks!
Bernie