1. Take any completed mgu - highlight some bars in the middle.
2. Generate that part of song using whatever melodist, chords only, voila.
Repeats double midi info each re-generation.

You can easily examine this with the event list editor.
As I said I tried this with 2012, 2011.5 and 2011. Same result using different mgus
and different melodists.

By the way I often write music for solo piano using BB. I know BB is not really designed for this but using BB
is how I learned some 15 years ago and I'm too old to change. I have owned every version of
BB since v7.
The waltz in question is 218 bars long and lasts 7 minutes. That's a lot of notes, pedals
and tempo changes to be duplicated. The music was exported to midi, imported into RealBand (quicker)
and the duplicates hand deleted. After rechecking, all of the waltzes in my last Cd have
some duplicate control info.
I use BB because I am technically inept as an instrumentalist and at music theory but I am stubborn.
Writing pretty things is what I do as a retired hobbyist - generally several hours a day.