Thanks for your reply Geoff and apologies for the delay in getting back to you about my arcane question!.
Have done some further, let's say "experimenting", and have determined the following:-
• cc87 is written to a type 0 midi file (and is always set to a value that matches the adjacent cc7 Vol control, per track,) when the file is saved by the Technics KN6500
• If there is no pre-existing cc7 event present on the track then the KN6500 does NOT add one of its "own" cc87 events.
• The cc87 event can NOT be seen when interrogating the KN6500 on board sequencer in edit mode.
• The cc87 event CAN be seen to exist when viewed in a Third-Party editing programme, in this case PowerTracks - see the pic with the event highlighted by the yellow arrow.
• A lot of midi control messages, including cc87, are dumped to the track header, (all at 1:0:000) if the keyboard's "Panel Header" mode of saving is utilized. This stores all the keyboard settings and are assigned to the various cc#s you can see in the other pic attached and includes solo settings. sound DSP, portamento settings, EQ, bend sensitivity, key shift, modulation, filter resonance, drawbar settings and all that lovely stuff that effectively "screenshots", in MIDI, how the keys were set at the time of saving. Interestingly, as you may see from the pic, none of the controllers are named other than the usual suspects, plus the mysterious "VolNodeCtrl".
• cc87 is recognised by the KN6500 but is not transmitted.
Have searched for a Technics MIDI manual but to no avail as far as cc87, or rather Technics use of it is concerned. I Googled it all again tonight and got a bit excited when I found a search item that read "Midi Vol Node cc87" only to find that it was pointing at this thread!
The only "volume" related aspect of the keyboard's physical controls that I can see that might be relevant is that the volume output control for the sequencer is independent from the machine's main volume slider. However, moving the sequencer slider will produce matching movement on the on-screen virtual slider for Auto Accompaniment, if it is turned on.
So.... I'm going to take a bit of a stab in the dark and attempt to answer my own question! Technics use of cc87 Volume Node Control communicates a dynamic level control to its own Autoplay Chord system where a midi file is in charge of the accompaniment patterns, but also (possibly unintentionally) pops a cc87 into a track if it finds a cc7 present in a standard midi file
being saved on the Technics.
Unless someone out there actually knows?!
As you say Geoff, any other device is going to ignore an unspecified controller and I guess that's the point, it gave, and gives, other device manufacturers options. Although in this case the allocation of a controller name gave me the impression it wasn't unspecified, hence the question.