Well, here is an update on my progress:
I have managed to make a tune with my mini midi controller. I have had to use the controller's software because I could not find a way in BIAB to make the controller sound when I press the key, not after supper. I then managed to get the midi file onto the melody track in BIAB and used the notation editor to adjust the time and notes and... anyway getting that far took hours! The melody time kept shifting; it seems when you save you have to choose the "save patches....etc.
Then I got an MGU file which I was happy with and, like always, exported to MP3. which is my preferred format for backing tracks and Lo and Behold......there is no melody.
Imagine my dismay?
Now, please, how can I convince Band in a box that the melody track which contains the midi tune, is part of the backing track?