In the interests of minimizing confusion, a combined midi and audio track is a "
Simple Instrument Track".
It's simple because it occupies only one track visually, but in fact incorporates one midi and one audio track. Exactly as if you set up one midi and one audio track separately for a soft synth. In fact, you can easily convert back and forth between (1 midi + 1 audio) and 1 "Simple Instrument Track".
Normally, the Simple Instrument Track displays the midi track, but if you freeze the synth (converting the midi to audio) then the audio track is displayed, until you unfreeze. I'm find them handy, others don't.