Yeah it is more logical to start with MIDI and add audio last, I Melodyne but have not used it yet.

Here is a sample of what Band in a box does not support

https://www.youtube.com/watch?v=GNsaos5eACU

Band in box kicks in at 1:32

The chords prior to that have very good voice leading (based on mathematics) and some quartal chords, so I used Korg Karma arpeggiator.

This one is more professional
https://www.youtube.com/watch?v=yjZvp92iO0I

3/4 is band in a box but bass is tweeked to follow the lead sheet.
You can tell at 7:08 that is not BiaB. Some of the harp sounds are Korg Karma generated.