I found a possible solution to my problem. Please let me know if I'm on the right track...
I loaded up my song on PT with different instruments on different tracks. I set my keyboard/synth to performance mode. I plugged a cable into the outputs on the back of the keyboard/synth, and plugged that into the mic input of my PC. I then loaded a different audio program on my PC to record. I set it to record and it recorded all the instruments that I wanted. It appears that the sound is being processed by the keyboard/synth, running it through the midi patches selecyted on the synth (not PT) and outputting it from the synth to the audio out on the synth, then into record on my PC. The only issuer now is my one audio track is not being output - only the midi tracks.

Help appreciated!

Bernie