OK I think it went sideways when though meaning well Jonesey Gave a different example.
the trouble is ---- there is more than one way to achieve most tasks in Sonar ( or any DAW)
abacab's post #2 was the way I would have done it too. I don't use simple instrument tracks which is a combonation audio and midi track, I find that restricting if I want to change the VST I'm using. Much simpler to use a pure midi track and then you can easily change it's output to different synths while looking for the right sounds.
so in less detail of what abacab has clearly described already.
Insert tts-1 choose the single output option. Other options can be yours to use later once you get the hang of it.
You insert as many midi tracks as you will need. A fast way is use the "insert multiple tracks"
And now it's a matter of changing the dialog in all those little boxes in the track pane or inspector.
Input= Midi port or USB from controller.
Output= TTS_1 (or any soft synth)
Midi channel = each track will be assigned a different channel. ( 1: Cakewalk TTS_1 ) ( 2: Cakewalk TTS_1 )
Bank selection= choose bank 0 to start, later you can explore sounds in other banks
Patch or Program = select the sound for that channel for each track.
Now you just set the track in record mode for the instrument you wish to use and go at it.
If you want to see what TTS-1 can do download a midi file and "open it" TTS-1 will automatically load with all 16 tracks and all the instruments and play the way the composer wanted it to sound.
https://freemidi.org/download-4224-silver-bells-christmas Terribly played like most of them but I was in a hurry :)