So the Audio Track is just another track but with the name "Audio".
Audio track, Thru track, Melody track or Utility tracks are all the same, if I well understand ...
Well, not really (pas vraiment). The way I understand it is this:
The audio track has audio.
The Melody, Soloist, and Thru Tracks are MIDI.
Other instrument tracks (bass, piano, drums, guitar) may be either audio (RealTracks) or MIDI, depending on the style you choose.
The Utility tracks start off empty and become audio from whatever you move to them.
It is true that BIAB is evolving in this area but we are not yet at the point where all tracks behave identically.
And of course, user AudioTrack who replied is none of the above; his name is Trevor