Tuned and festival instruments are practically the same sound wise, but they're still separate items.
These are just what I've noticed from my old MMLs, but to me the piano, violin, and cello are louder than they were before. All the old wind instruments aside from tuba (flute, whistle, chalumeau, and roncadora) sound more quiet than before (v15 flute is no longer cancer for example). Cymbals seem louder than they did before too.
This is just from me observing how some of my songs sound before and after the Music Q patch. If anyone else can confirm the changes that have been made, that'd be great.