I've been composing music for a LONG time. I first became acquainted with BIAB in the late 80's. I had to do 16 nursery rhymes with all different singers, and each song in a different style. And had 3 weeks to do it. This would have been totally impossible. I had seen mention of BIAB. I bought it - and completed the task on time. The client was amazed and delighted. Then I worked for a music library service, which also demanded variety, and fast turn around time. At that point I began listening to music libraries, paying close attention to TV commercials. I could pick out some tunes that also had used Band in a Box to do the job.

To make the song more sophisticated, and not sound computer generated, I began with using a few different styles for the same song . I started using the bass part from one style, guitar from another.. I also would record the song with different blue and green tabs (verse/chorus) The chorus is usually busier. I would sometimes create 4 versions with different styles, drag the 4 guitar parts into Logic. Cut them up into one bar sections, and switch between them as the song progressed.
Because a few instruments were changing parts frequently and in different spots, there was no more, 'everything changed at once' effect.

I generally liked the bass parts that came up. Melodies are good/sometimes great. Also create a part, I would never have thought of.

However a very important benefit of BIAB - is that it can be one of the best teaching tools available. I always imported BIAB midi files into Logic Pro, and began using the Score editor with all instruments displayed. Although Logic's score editor is not the most user friendly.. It had a very strong influence on my arranging, and compositions.

I always created a version of the song in the utility organ chords. This gives you a straight full blocked chords track. I would also use this to drive keyboard arrangers (Tyros 3 - Genos at this point).
I would often create a part with BIAB and then somewhat learn it and play it by hand. Thus teaching me different rhythmic patterns, various instruments use. Also great for getting soloing ideas.

Also in the creation of a song, I play around a fair amount with chord substitutions. BIAB is excellent for this. Because to understand the value of certain chords, you need to have several instruments. No more building a song from scratch, figuring out 5 parts to realize there were several 'bad choices of chords'.

Because BIAB has so many features, it does take a while to work thru them. But it is time well spent.