M@
I looked through the sourcecode a bit and found these passages:
// ACT Button
   pmsg = createMidiMsg( _T("ACT"), BID_Act );
...
......and understand that they somehow generate midi-notes 71 and 43 but not more than that.
How or what happens then....no clue.

That does not create MIDI message in terms of what you think.... It just add a definition of that message into the list and map it to BID_Act constant. When it is received, VS code knows that BID_Act is pressed.
 
Well, in case you explain what your target is, may be I can give you a good advise in which direction to go. It can take many moons before you understand Tacoma code. If you just want change particular functionality, I can say precisely where to look. If you want it to do completely different things from what it does now, you can be much faster with AZCtrl. If you just want understand how all that works, I can just continue with small tips. And I can be silent as well

azslow3
May be you reconsider and finish some album instead

that's good advice that I take away from this thread ... nevertheless I keep listening in :-)

Hi Azslow3,
Thanks for your offer to assist with some tips, but as I am not a programmer & must be realistic that I cannot do anything with these source-codes . However, my last post & your reply to my previous post 'missed each other' as it took a while to type. I'd still be interested to hear your opinion on that "vst-parameter" window in sonar.

You are right, I have skipped your previous message...
 
That window is the default VST parameter window which is appeared in case VST has NO property page specified.
With ProChannels modules (as you have already noticed) it is a bit buggy... Most modules produce and error in attempt to use it. I think the proper way is to submit future request to save ProChannel modules preset. Technically Sonar IS saving these presets into the project. It is just about a dialog to save them separately (as they do with other VST and even Control Surface plug-ins presets).
 
About the "back door". Control Surface SDK has several functions for "Context", including "Open"/"Close". You VS is doing that. "ACT MIDI" plug-in can do this too (command name is "Open current plug-in"). AZ Controller can not do that on purpose (I try to detect that ProChannel is in focus) to avoid error windows
 
Since that is not a "Sonar Command", it can not be mapped to keyboard. You need some controller for that.