Also... on a much more advanced level...
If you do want to work with midi in BIAB, it's possible to load the midi onto the Melody or Soloist track and then transfer it elsewhere, channel by channel. See the image below that shows how to use "Copy special | Copy/Move Tracks".
If you transfer it to any track other than the Melody or Soloist, though, make sure you
freeze the track because if you (re)generate BIAB, the copied/moved track will be over-written unless it is frozen.
Regards,
Noel