You can't SAVE a midi track to an audio track, Bill. You have to set up an empty audio track in your daw and then route the midi track to the audio track and then RECORD it as audio. That's the way to do it if you want the midi track to be an audio track.

There should be no problem to bounce the two tracks together, and be able to hear the sound from both, though. If that's the issue, make sure you have marked both track's to be bounced. Remember midi is just numbers, so it doesn't record any actual sound, therefore you also need an virtual instrument to create sound on your midi track, but that should be there if you can hear sound.

Im not a cubase/tracktion user, so I can't be more specific with that.