This can be done already using a combination of generate the song using "the default chord sheet" then freeze all tracks and then, say, unfreeze the piano part and change the chords to suit or change part markers for drum fills, regenerate and repeat as necessary. Also works with holds, shots and pushes. Requires a good memory tho' to remember the original chords! or to save each incremental song with a logical name

I thought of this a few weeks ago and am having great fun developing a logical way to work, if that is possible.

Alyn