Hi people
I persuaded myself that I needed to upgrade from Music Creator 4 to 7 as I had gone to Windows 10.  I've had an absolute nightmare with it.  I've decided I'm probably using it incorrectly for my purposes.  The main reason I use it is to create MIDI files, either for lead sheets or to insert into Band-in-a-box sequences. I insert notes onto a staff view.  Having, with much difficulty, found that a lot of the staff view menu items have moved to the main view, I've just tried to change an instrument on a MIDI track.  Can I find an icon to click? Can I ********
 
I find the MIDI documentation very difficult to access and search and the MIDI parts seem hidden or missing
 
Am I doing something wrong?

changing which instrument is playing on a MIDI track hasn't changed from the first MCPro version until now.  yes, a lot of the MIDI and staff stuff has been moved around, but the basic instrument selection hasn't changed - that's always been on the track properties.
 
what are you using for MIDI output?  where are you trying to change the instrument?

I've got coolsoft midi synth and timbresofheaven soundfont
 
The instruments are set to soundfont device in the MIDI allocation.  The problem could be that I don't understand the next step to change an instrument.  I can't find anything on the track view that admits to opening track properties 
 

I've got one step further.  Having allocated the MIDI Device to CoolsoftvirtualMIDIsynth and then allocated each track to use soundfontdevice as the instrument
There is a button called DEFINE.  Yoiu and up with a double pane window.  On the left you can see the soundfontdevice and on the right you can see names like general MIDI.  there doesn't seem to be any choosing mechanism and I still don't see a way of allocating an instrument to a track!!
 

unfortunately you're choosing to use a soundfont player, which means you're not going to be able to choose the instruments by changing settings in MC, you have to change them in the soundfont player itself, which you're beginning to understand.  that DEFINE button is not part of MC, it must be part of the soundfont player you're using.  
 
also unfortunately, I can't help much with that soundfont player because I'm not familiar with it (and I really just don't have time to download it and fiddle with it to help - it's not something I would use anyway).
 
is there a reason you're trying to use this particular soundfont player instead of using some of the tools included with MC?  MC includes Cakewalk SoundCenter which has some really good sounds in it.  it also has SI Drums and maybe some other SI instruments, I can't remember for certain which ones came with MC7 since I have Sonar as well (they all get installed and are usable on both platforms).
 

Music Creator 7 has SoundCenter with four instruments: strings, drums, bass and piano.
 
 Music Creator 7 also includes the TTS-1 virtual sound module.  The TTS-1 has built-in General Midi 1 (GM1), GM2, Roland GS and Yamaha XG lite instrument sounds (patches).  The TTS-1 is 128 voice polyphonic (can play up to 128 sounds at one time) and has chorus and reverb effects built-in.
 
We can help you easier when you are using tools that ship with the product.  You maybe familiar with TTS-1 as either it or a similar product the Virtual Sound Canvas (VSC) shipped with MC4.